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 (40209)
Use after free in Browser UI in Google Chrome on Chrome prior to 92.0.4515.131 allowed a remote attacker to potentially exploit heap corruption via physical access to the device. Rated medium severity (CVSS 6.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Use after free in Page Info UI in Google Chrome prior to 92.0.4515.131 allowed a remote attacker to potentially exploit heap corruption via physical access to the device. Rated medium severity (CVSS 6.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
Use after free in File System API in Google Chrome prior to 92.0.4515.131 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
In ForgeRock Access Management (AM) before 7.0.2, the SAML2 implementation allows XML injection, potentially enabling a fraudulent SAML 2.0 assertion. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the way Cisco UCS Manager software handles SSH sessions could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, low attack complexity.
A vulnerability in the implementation of the system login block-for command for Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a login process to unexpectedly restart,. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Write vulnerability could allow attackers to write data beyond allocated buffer boundaries leading to code execution or crashes.
A vulnerability in the MPLS Operation, Administration, and Maintenance (OAM) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS). Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A vulnerability in the VXLAN Operation, Administration, and Maintenance (OAM) feature of Cisco NX-OS Software, known as NGOAM, could allow an unauthenticated, remote attacker to cause a denial of. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A vulnerability in the Multi-Pod or Multi-Site network configurations for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated,. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
A denial of service vulnerability exists in the ASDU message processing functionality of MZ Automation GmbH lib60870.NET 2.2.0. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A vulnerability in Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, remote attacker to cause a queue wedge on a leaf switch,. Rated high severity (CVSS 8.6), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Knot Resolver before 5.3.2 is prone to an assertion failure, triggerable by a remote attacker in an edge case (NSEC3 with too many iterations used for a positive wildcard proof). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Rated high severity (CVSS 8.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
detect-character-encoding is an open source character encoding inspection library. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A logic issue was addressed with improved state management. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
A denial of service issue was addressed with improved state handling. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
A use after free issue was addressed with improved memory management. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe After Effects version 18.2 (and earlier) is affected by an Our-of-bounds Read vulnerability when parsing a specially crafted file. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe After Effects version 18.2 (and earlier) is affected by an Our-of-bounds Read vulnerability when parsing a specially crafted file. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Acrobat Reader DC versions versions 2021.001.20155 (and earlier), 2020.001.30025 (and earlier) and 2017.011.30196 (and earlier) are affected by an Use After Free vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Acrobat Reader DC versions versions 2021.001.20155 (and earlier), 2020.001.30025 (and earlier) and 2017.011.30196 (and earlier) are affected by an Use After Free vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe After Effects version 18.2 (and earlier) is affected by an Our-of-bounds Read vulnerability when parsing a specially crafted file. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe After Effects version 18.2 (and earlier) is affected by an Our-of-bounds Read vulnerability when parsing a specially crafted file. Rated high severity (CVSS 7.1), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Adobe After Effects version 18.2 (and earlier) is affected by a Null pointer dereference vulnerability when parsing a specially crafted file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Acrobat Reader DC versions versions 2021.001.20155 (and earlier), 2020.001.30025 (and earlier) and 2017.011.30196 (and earlier) are affected by an Use After Free vulnerability. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the string data and a field holding the buffer length. Rated high severity (CVSS 7.4), this vulnerability is remotely exploitable, no authentication required. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.
All versions of package transpile are vulnerable to Denial of Service (DoS) due to a lack of input sanitization or whitelisting, coupled with improper exception handling in the .to() function. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A Buffer Overflow vulnerabilty exists in Miniftpd 1.0 in the do_mkd function in the ftpproto.c file, which could let a remote malicious user cause a Denial of Service. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. Public exploit code available and no vendor patch available.
There is a denial of service vulnerability in Huawei products. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
There is a denial of service vulnerability in some huawei products. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
XStream is a simple library to serialize objects to XML and back again. Rated medium severity (CVSS 6.3), this vulnerability is remotely exploitable. Public exploit code available.
A Denial-of-Service (DoS) vulnerability was discovered in all versions of F-Secure Atlant whereby the SAVAPI component used in certain F-Secure products can crash while scanning fuzzed files. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
OpenStack Neutron before 16.4.1, 17.x before 17.1.3, and 18.0.0 allows hardware address impersonation when the linuxbridge driver with ebtables-nft is used on a Netfilter-based platform. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) before 1.18.5 and 1.19.x before 1.19.3 has a NULL pointer dereference in kdc/do_tgs_req.c via a FAST inner body that lacks a server. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity.
Acrobat Reader DC versions 2021.005.20054 (and earlier), 2020.004.30005 (and earlier) and 2017.011.30197 (and earlier) are affected by a Null pointer dereference vulnerability. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
Acrobat Reader DC versions 2021.005.20054 (and earlier), 2020.004.30005 (and earlier) and 2017.011.30197 (and earlier) are affected by a Null pointer dereference vulnerability. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
Adobe Illustrator version 25.2.3 (and earlier) is affected by a Use After Free vulnerability when parsing a specially crafted file. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. No vendor patch available.
A vulnerability was discovered in GitLab versions before 14.0.2, 13.12.6, 13.11.6. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.
The web server in InterNiche NicheStack through 4.0.1 allows remote attackers to cause a denial of service (infinite loop and networking outage) via an unexpected valid HTTP request such as OPTIONS. 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 tcp_pulloutofband() in tcp_in.c in HCC embedded InterNiche 4.0.1. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
A vulnerability in the Link Layer Discovery Protocol (LLDP) implementation for the Cisco Video Surveillance 7000 Series IP Cameras firmware could allow an unauthenticated, adjacent attacker to cause. Rated medium severity (CVSS 6.5), this vulnerability is no authentication required, low attack complexity.
A vulnerability in the Universal Plug-and-Play (UPnP) service of Cisco Small Business RV110W, RV130, RV130W, and RV215W Routers could allow an unauthenticated, remote attacker to execute arbitrary. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
In BIND 9.16.19, 9.17.16. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
liveMedia/FramedSource.cpp in Live555 through 1.08 allows an assertion failure and application exit via multiple SETUP and PLAY commands. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
All versions of package trim-off-newlines are vulnerable to Regular Expression Denial of Service (ReDoS) via string processing. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
jsoup is a Java library for working with HTML. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
In memory management driver, there is a possible system crash due to a missing bounds check. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
In memory management driver, there is a possible system crash due to improper input validation. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
In memory management driver, there is a possible system crash due to improper input validation. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
In memory management driver, there is a possible system crash due to improper input validation. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
In memory management driver, there is a possible system crash due to improper input validation. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity. No vendor patch available.
User controlled `request.getHeader("Referer")`, `request.getRequestURL()` and `request.getQueryString()` are used to build and run a regex expression. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
ced detects character encoding using Google’s compact_enc_det library. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
A buffer overflow vulnerability in the TCP/IP stack of Juniper Networks Junos OS allows an attacker to send specific sequences of packets to the device thereby causing a Denial of Service (DoS). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An issue present in lowering/register allocation could have led to obscure but deterministic register confusion failures in JITted code that would lead to a potentially exploitable crash. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
An integer overflow vulnerability in the calloc() function of the C runtime library of affected versions of BlackBerry® QNX Software Development Platform (SDP) version(s) 6.5.0SP1 and earlier, QNX OS. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
Node.js before 16.6.1, 14.17.5, and 12.22.5 is vulnerable to a use after free attack where an attacker might be able to exploit the memory corruption, to change process behavior. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
The deferred_image_processing (aka Deferred image processing) extension before 1.0.2 for TYPO3 allows Denial of Service via the FAL API because of /var/transient disk consumption. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
NVIDIA DCGM, all versions prior to 2.2.9, contains a vulnerability in the DIAG module where any user can inject shared libraries into the DCGM server, which is usually running as root, which may lead. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.
The MiCollab Client service in Mitel MiCollab before 9.3 could allow an unauthenticated user to gain system access due to improper access control. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
The AWV and MiCollab Client Service components in Mitel MiCollab before 9.3 could allow an attacker to perform a Man-In-the-Middle attack by sending multiple session renegotiation requests, due to. Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required. No vendor patch available.
The RISC-V Instruction Set Manual contains a documented ambiguity for the Machine Trap Vector Base Address (MTVEC) register that may lead to a vulnerability due to the initial state of the register. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.
A use-after-free in function hci_sock_bound_ioctl() of the Linux kernel HCI subsystem was found in the way user calls ioct HCIUNBLOCKADDR or other way triggers race condition of the call. Rated medium severity (CVSS 6.4). Public exploit code available.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. 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.
TensorFlow is an end-to-end open source platform for machine learning. 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.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. This Use After Free vulnerability could allow attackers to access freed memory to execute arbitrary code or crash the application.
TensorFlow is an end-to-end open source platform for machine learning. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.
TensorFlow is an end-to-end open source platform for machine learning. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.