Denial of Service
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
How It Works
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions. Attackers exploit asymmetry: minimal attacker effort produces disproportionate resource consumption on the target. Application-level attacks use specially crafted inputs that trigger expensive operations—a regex engine processing malicious patterns can backtrack exponentially, or XML parsers recursively expand entities until memory exhausts. Network-level attacks flood targets with connection requests or amplify traffic through reflection, but application vulnerabilities often provide the most efficient attack surface.
The attack typically begins with reconnaissance to identify resource-intensive operations or unprotected endpoints. For algorithmic complexity attacks, adversaries craft inputs hitting worst-case performance—hash collision inputs filling hash tables with collisions, deeply nested JSON triggering recursive parsing, or pathological regex patterns like (a+)+b against strings of repeated 'a' characters. Resource exhaustion attacks open thousands of connections, upload massive files to unbounded storage, or trigger memory leaks through repeated operations. Crash-based attacks target error handling gaps: null pointer dereferences, unhandled exceptions in parsers, or assertion failures that terminate processes.
Impact
- Service unavailability preventing legitimate users from accessing applications during attack duration
- Revenue loss from downtime in e-commerce, SaaS platforms, or transaction processing systems
- Cascading failures as resource exhaustion spreads to dependent services or database connections pool out
- SLA violations triggering financial penalties and damaging customer trust
- Security team distraction providing cover for data exfiltration or intrusion attempts running concurrently
Real-World Examples
CVE-2018-1000544 in Ruby's WEBrick server allowed ReDoS through malicious HTTP headers containing specially crafted patterns that caused the regex engine to backtrack exponentially, freezing request processing threads. A single attacker could saturate all available workers.
Cloudflare experienced a global outage in 2019 when a single WAF rule containing an unoptimized regex hit pathological cases on legitimate traffic spikes. The .*(?:.*=.*)* pattern exhibited catastrophic backtracking, consuming CPU cycles across their edge network until the rule was disabled.
CVE-2013-1664 demonstrated XML bomb vulnerabilities in Python's XML libraries. Attackers uploaded XML documents with nested entity definitions-each entity expanding to ten copies of the previous level. A 1KB upload could expand to gigabytes in memory during parsing, crashing applications instantly.
Mitigation
- Strict input validation enforcing size limits, complexity bounds, and nesting depth restrictions before processing
- Request rate limiting per IP address, API key, or user session with exponential backoff
- Timeout enforcement terminating operations exceeding reasonable execution windows (typically 1-5 seconds)
- Resource quotas limiting memory allocation, CPU time, and connection counts per request or tenant
- Regex complexity analysis using linear-time algorithms or sanitizing patterns to eliminate backtracking
- Circuit breakers automatically rejecting requests when error rates or latency thresholds indicate degradation
- Load balancing and autoscaling distributing traffic across instances with automatic capacity expansion
Recent CVEs (5589)
An Improper Following of Specification by Caller vulnerability in web management (J-Web, Captive Portal, 802.1X, Juniper Secure Connect (JSC) of Juniper Networks Junos OS on SRX Series, EX Series,. Rated high severity (CVSS 8.7), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An Improper Check for Unusual or Exceptional Conditions vulnerability in routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, logically adjacent. Rated medium severity (CVSS 6.0), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
A Missing Release of Memory after Effective Lifetime vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS and Junos OS Evolved allows an adjacent, unauthenticated attacker. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
An Improper Check for Unusual or Exceptional Conditions vulnerability in the pfe (packet forwarding engine) of Juniper Networks Junos OS on MX Series causes a port within a pool to be blocked leading. Rated high severity (CVSS 8.7), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A Buffer Access with Incorrect Length Value vulnerability in the jdhcpd daemon of Juniper Networks Junos OS, when DHCP snooping is enabled, allows an unauthenticated, adjacent, attacker to send a. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Allocation of Resources Without Limits or Throttling, Incorrect Authorization vulnerability in Drupal WEB-T allows Excessive Allocation, Content Spoofing.0.0 before 1.1.0. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
XGrammar is an open-source library for efficient, flexible, and portable structured generation. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Allocation of Resources Without Limits vulnerability could allow attackers to exhaust system resources through uncontrolled allocation.
The Apollo Router Core is a configurable, high-performance graph router written in Rust to run a federated supergraph that uses Apollo Federation 2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
DNN (formerly DotNetNuke) is an open-source web content management platform (CMS) in the Microsoft ecosystem. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Adobe Framemaker versions 2020.8, 2022.6 and earlier are affected by a NULL Pointer Dereference vulnerability that could result in an application denial-of-service. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe Framemaker versions 2020.8, 2022.6 and earlier are affected by a NULL Pointer Dereference vulnerability that could result in an application denial-of-service. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Windows Common Log File System Driver contains a use-after-free enabling local privilege escalation, exploited in the wild in April 2025. CLFS driver vulnerabilities have become a recurring Windows kernel exploit target.
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office Word allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.3), this vulnerability is low attack complexity. No vendor patch available.
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office Word allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Office allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Windows Digital Media allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
Use after free in Windows Shell allows an unauthorized attacker to execute code locally. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Windows Hyper-V allows an authorized attacker to execute code over a network. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable. No vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 33.1% and no vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 33.1% and no vendor patch available.
Use after free in Remote Desktop Gateway Service allows an unauthorized attacker to execute code over a network. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Use after free in Windows Digital Media allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
Uncontrolled resource consumption in Windows HTTP.sys allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 42.4% and no vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 39.5% and no vendor patch available.
Uncontrolled resource consumption in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 42.4% and no vendor patch available.
Use after free in Windows Digital Media allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
Animate versions 24.0.7, 23.0.10 and earlier are affected by a Use After Free vulnerability that could result in arbitrary code execution in the context of the current user. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
After Effects versions 25.1, 24.6.4 and earlier are affected by a NULL Pointer Dereference vulnerability that could result in an application denial-of-service. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Use after free in Windows Win32K - GRFX allows an unauthorized attacker to elevate privileges over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Allocation of resources without limits or throttling in ASP.NET Core allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 47.0% and no vendor patch available.
Use after free in Windows Win32K - GRFX allows an authorized attacker to elevate privileges locally. Rated medium severity (CVSS 6.7). No vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 42.4% and no vendor patch available.
Use after free in RPC Endpoint Mapper Service allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
Uncontrolled resource consumption in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 44.1% and no vendor patch available.
Use after free in Windows Remote Desktop Services allows an unauthorized attacker to execute code over a network. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Use after free in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to execute code over a network. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Use after free in Windows LDAP - Lightweight Directory Access Protocol allows an unauthorized attacker to execute code over a network. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 42.4% and no vendor patch available.
Uncontrolled resource consumption in Windows Cryptographic Services allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 42.4% and no vendor patch available.
Use after free in Windows Digital Media allows an authorized attacker to elevate privileges locally. Rated high severity (CVSS 7.0). No vendor patch available.
Uncontrolled resource consumption in Windows Standards-Based Storage Management Service allows an unauthorized attacker to deny service over a network. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 35.9% and no vendor patch available.
Null pointer dereference in some Zoom Workplace Apps for Windows may allow an authenticated user to conduct a denial of service via network access. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Null pointer dereference in some Zoom Workplace Apps for Windows may allow an authenticated user to conduct a denial of service via network access. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
An issue was discovered in Elasticsearch, where a large recursion using the Well-KnownText formatted string with nested GeometryCollection objects could cause a stackoverflow. Rated medium severity (CVSS 4.9), this vulnerability is remotely exploitable, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
A flaw was discovered in Elasticsearch, where a large recursion using the innerForbidCircularReferences function of the PatternBank class could cause the Elasticsearch node to crash. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
An issue has been identified where a specially crafted request sent to an Observability API could cause the kibana server to crash. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
bep/imagemeta is a Go library for reading EXIF, IPTC and XMP image meta data from JPEG, TIFF, PNG, and WebP files. Rated medium severity (CVSS 6.9), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
bep/imagemeta is a Go library for reading EXIF, IPTC and XMP image meta data from JPEG, TIFF, PNG, and WebP files. Rated medium severity (CVSS 6.9), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Shopware is an open commerce platform. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In the Linux kernel, the following vulnerability has been resolved: devlink: fix xa_alloc_cyclic() error handling In case of returning 1 from xa_alloc_cyclic() (wrapping) ERR_PTR(1) will be returned,. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
In the Linux kernel, the following vulnerability has been resolved: dpll: fix xa_alloc_cyclic() error handling In case of returning 1 from xa_alloc_cyclic() (wrapping) ERR_PTR(1) will be returned,. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
In the Linux kernel, the following vulnerability has been resolved: mm/migrate: fix shmem xarray update during migration A shmem folio can be either in page cache or in swap cache, but not at the. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state There are several problems with the way hyp code lazily saves the. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
In the Linux kernel, the following vulnerability has been resolved: Revert "arm64: dts: qcom: sdm845: Affirm IDR0.CCTW on apps_smmu" There are reports that the pagetable walker cache coherency is not. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
In the Linux kernel, the following vulnerability has been resolved: ARM: dts: bcm2711: Fix xHCI power-domain During s2idle tests on the Raspberry CM4 the VPU firmware always crashes on xHCI. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
In the Linux kernel, the following vulnerability has been resolved: regulator: dummy: force synchronous probing Sometimes I get a NULL pointer dereference at boot time in kobject_get() with the. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
The Apollo Router Core is a configurable, high-performance graph router written in Rust to run a federated supergraph that uses Apollo Federation 2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The Apollo Router Core is a configurable, high-performance graph router written in Rust to run a federated supergraph that uses Apollo Federation 2. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Apollo Gateway provides utilities for combining multiple GraphQL microservices into a single GraphQL endpoint. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Allocation of Resources Without Limits vulnerability could allow attackers to exhaust system resources through uncontrolled allocation.
Apollo Gateway provides utilities for combining multiple GraphQL microservices into a single GraphQL endpoint. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Allocation of Resources Without Limits vulnerability could allow attackers to exhaust system resources through uncontrolled allocation.
ts-asn1-der is a collection of utility classes to encode ASN.1 data following DER rule. Rated medium severity (CVSS 6.9), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
apollo-compiler is a query-based compiler for the GraphQL query language. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Buffer Overflow vulnerability in gdal 3.10.2 allows a local attacker to cause a denial of service via the OGRSpatialReference::Release function. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the cfl_list_size in cfl_list.h:165. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.
An attacker can publish a zone containing specific Resource Record Sets. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In Modem, there is a possible system crash due to improper input validation. Rated medium severity (CVSS 6.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
In NetX HTTP server functionality of Eclipse ThreadX NetX Duo before version 6.4.3, an attacker can cause a denial of service by specially crafted packets. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, low attack complexity.
In NetX HTTP server functionality of Eclipse ThreadX NetX Duo before version 6.4.3, an attacker can cause an integer underflow and a subsequent denial of service by writing a very large file, by. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, low attack complexity.
In NetX Duo component HTTP server functionality of Eclipse ThreadX NetX Duo before version 6.4.3, an attacker can cause an integer underflow and a subsequent denial of service by writing a very large. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, low attack complexity.
A floating-point exception in the PSStack::roll function of Poppler before 25.04.0 can cause an application to crash when handling malformed inputs associated with INT_MIN. Rated medium severity (CVSS 4.0), this vulnerability is no authentication required, low attack complexity. Public exploit code available.
The ZoomSounds - WordPress Wave Audio Player with Playlist plugin for WordPress is vulnerable to unauthorized modification of data that can lead to a denial of service due to a missing capability. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
An issue in fluent-bit v.3.7.2 allows a local attacker to cause a denial of service via the function consume_event. Rated medium severity (CVSS 5.5). Public exploit code available and no vendor patch available.
Improper isolation of users in M-Files Server version before 25.3.14549 allows anonymous user to affect other anonymous users views and possibly cause a denial of service. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Allocation of resources without limits or throttling issue exists in HMI ViewJet C-more series and HMI GC-A2 series, which may allow a remote unauthenticated attacker to cause a denial-of-service. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Use after free in Microsoft Edge (Chromium-based) allows an authorized attacker to execute code over a network. Rated high severity (CVSS 7.6), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
This vulnerability affects Snowplow Collector 3.x before 3.3.0 (unless it’s set up behind a reverse proxy that establishes payload limits). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Uncontrolled Resource Consumption vulnerability could allow attackers to cause denial of service by exhausting system resources.
An issue was discovered affecting Enrich 5.1.0 and below. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue was discovered in Iglu Server 0.13.0 and below. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability, which was classified as problematic, has been found in Tenda AC23 16.03.07.52. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
XZ Utils provide a general-purpose data-compression library plus command-line tools. Rated high severity (CVSS 8.7), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A flaw was found in libsoup. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
A flaw was found in libsoup. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: Fix error code in chan_alloc_skb_cb() The chan_alloc_skb_cb() function is supposed to return error pointers on error. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.