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 (5561)
In the Linux kernel, the following vulnerability has been resolved: um: init cpu_tasks[] earlier This is currently done in uml_finishsetup(), but e.g. with KCOV enabled we'll crash because some init code can call into e.g.
In the Linux kernel, the following vulnerability has been resolved: f2fs: ensure node page reads complete before f2fs_put_super() finishes Xfstests generic/335, generic/336 sometimes crash with the following message: F2FS-fs (dm-0): detect filesystem reference count leak during umount, type: 9, count: 1 ------------[ cut here ]------------ kernel BUG at fs/f2fs/super.c:1939!
In the Linux kernel, the following vulnerability has been resolved: drm/msm: adreno: fix deferencing ifpc_reglist when not declared On plaforms with an a7xx GPU not supporting IFPC, the ifpc_reglist if still deferenced in a7xx_patch_pwrup_reglist() which causes a kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 ...
In the Linux kernel, the following vulnerability has been resolved: scs: fix a wrong parameter in __scs_magic __scs_magic() needs a 'void *' variable, but a 'struct task_struct *' is given.
Libsndfile <=1.2.2 contains a memory leak vulnerability in the mpeg_l3_encoder_init() function within the mpeg_l3_encode.c file. [CVSS 5.3 MEDIUM]
Libsoup WebSocket implementations with unset maximum payload size limits are vulnerable to out-of-bounds memory reads during frame processing, potentially exposing sensitive data or causing application crashes. This vulnerability affects applications using non-default WebSocket configurations and requires no user interaction or authentication to exploit. No patch is currently available.
Sysax Multi Server 6.95 crashes when the admin password field receives 800 bytes, causing denial of service. PoC available.
AimOne Video Converter 2.04 Build 103 contains a buffer overflow vulnerability in its registration form that causes application crashes. Attackers can generate a 7000-byte payload to trigger the denial of service and potentially exploit the software's registration mechanism. [CVSS 6.5 MEDIUM]
GuardDog versions prior to 2.7.1 fail to validate decompressed file sizes when extracting Python package archives, enabling denial of service attacks through zip bomb payloads that can consume gigabytes of disk space from minimal compressed data. Public exploit code exists for this vulnerability, affecting users who rely on GuardDog to scan PyPI packages for malicious content. Upgrade to version 2.7.1 or later to remediate this flaw.
Go Ethereum (geth) nodes can be remotely crashed through maliciously crafted network messages, causing denial of service to affected network participants. An unauthenticated attacker on the network can exploit this vulnerability without user interaction to force vulnerable nodes offline. A patch is available in version 1.16.8 and later.
Go Ethereum nodes can be remotely crashed by unauthenticated attackers sending specially crafted network messages, resulting in denial of service. This network-based attack requires no user interaction and affects Golang and Go Ethereum implementations prior to version 1.16.8. A patch is available to remediate this high-severity vulnerability.
Kibana Fleet is vulnerable to denial of service through uncontrolled resource allocation when processing specially crafted bulk retrieval requests, allowing authenticated users with viewer-level privileges to exhaust server memory and crash the application. An attacker can trigger redundant database operations that consume resources without limits, rendering the service unavailable to all users. No patch is currently available for this vulnerability.
Kibana Fleet fails to limit resource allocation when processing specially crafted requests, allowing authenticated attackers to trigger excessive CPU and memory consumption that degrades or completely disables the service. The vulnerability affects Kibana deployments where users have authentication access, and no patch is currently available to remediate the issue.
Denial of Service in Prometheus and Kibana metricsets can be triggered by sending specially crafted malformed payloads to Graphite, Zookeeper, or Prometheus data sources due to improper array index validation and input validation flaws. An unauthenticated attacker on the network can exploit this to crash monitoring services without user interaction. No patch is currently available.
Tarteaucitronjs versions up to 1.29.0 is affected by inefficient regular expression complexity (redos) (CVSS 4.4).
Multiple out-of-bounds read vulnerabilities were identified in a system component responsible for handling certain data buffers. Due to insufficient validation of maximum buffer size values, the process may attempt to read beyond the intended memory region. [CVSS 5.3 MEDIUM]
Multiple out-of-bounds read vulnerabilities were identified in a system component responsible for handling certain data buffers. Due to insufficient validation of maximum buffer size values, the process may attempt to read beyond the intended memory region. [CVSS 5.3 MEDIUM]
Adobe Illustrator versions 29.8.3 and 30.0 and earlier are vulnerable to a null pointer dereference that enables local denial-of-service attacks when users open crafted files. An attacker can crash the application by supplying a malicious file, disrupting workflow for targeted users. No patch is currently available for this vulnerability.
A vulnerability affecting HPE Networking Instant On Access Points has been identified where a device processing a specially crafted packet could enter a non-responsive state, in some cases requiring a hard reset to re-establish services. [CVSS 7.5 HIGH]
Null pointer dereference in the MsgRegisterEvent() system call could allow an attacker with local access and code execution abilities to crash the QNX Neutrino kernel. [CVSS 6.2 MEDIUM]
In the Linux kernel, the following vulnerability has been resolved: ip6_gre: make ip6gre_header() robust Over the years, syzbot found many ways to crash the kernel in ip6gre_header() [1].
In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix the crash issue for zero copy XDP_TX action There is a crash issue when running zero copy XDP_TX action, the crash log is shown below.
In the Linux kernel, the following vulnerability has been resolved: drm/ttm: Avoid NULL pointer deref for evicted BOs It is possible for a BO to exist that is not currently associated with a resource, e.g. because it has been evicted.
Tenda AX-3 v16.03.12.10_CN was discovered to contain a stack overflow in the wanMTU2 parameter of the fromAdvSetMacMtuWan function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Tenda AX-3 v16.03.12.10_CN was discovered to contain a stack overflow in the wanSpeed2 parameter of the fromAdvSetMacMtuWan function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Tenda AX-3 v16.03.12.10_CN was discovered to contain a stack overflow in the cloneType2 parameter of the fromAdvSetMacMtuWan function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Tenda AX-3 v16.03.12.10_CN was discovered to contain a stack overflow in the serviceName2 parameter of the fromAdvSetMacMtuWan function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Tenda AX-3 v16.03.12.10_CN was discovered to contain a stack overflow in the mac2 parameter of the fromAdvSetMacMtuWan function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Tenda AX-1806 v1.0.0.1 was discovered to contain a stack overflow in the security_5g parameter of the sub_4CA50 function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
In the Linux kernel, the following vulnerability has been resolved: scsi: Revert "scsi: qla2xxx: Perform lockless command completion in abort path" This reverts commit 0367076b0817d5c75dfb83001ce7ce5c64d803a9.
In the Linux kernel, the following vulnerability has been resolved: net/mlx5: fw_tracer, Validate format string parameters Add validation for format string parameters in the firmware tracer to prevent potential security vulnerabilities and crashes from malformed format strings received from firmware.
In the Linux kernel, the following vulnerability has been resolved: ipvs: fix ipv4 null-ptr-deref in route error path The IPv4 code path in __ip_vs_get_out_rt() calls dst_link_failure() without ensuring skb->dev is set, leading to a NULL pointer dereference in fib_compute_spec_dst() when ipv4_link_failure() attempts to send ICMP destination unreachable messages.
In the Linux kernel, the following vulnerability has been resolved: media: iris: Add sanity check for stop streaming Add sanity check in iris_vb2_stop_streaming. If inst->state is already IRIS_INST_ERROR, we should skip the stream_off operation because it would still send packets to the firmware.
In the Linux kernel, the following vulnerability has been resolved: platform/chrome: cros_ec_ishtp: Fix UAF after unbinding driver After unbinding the driver, another kthread `cros_ec_console_log_work` is still accessing the device, resulting an UAF and crash.
In the Linux kernel, the following vulnerability has been resolved: net/hsr: fix NULL pointer dereference in prp_get_untagged_frame() prp_get_untagged_frame() calls __pskb_copy() to create frame->skb_std but doesn't check if the allocation failed.
In the Linux kernel, the following vulnerability has been resolved: inet: frags: flush pending skbs in fqdir_pre_exit() We have been seeing occasional deadlocks on pernet_ops_rwsem since September in NIPA.
Service Workers in Mozilla Firefox and Thunderbird versions below 147 are vulnerable to remote denial-of-service attacks that require no user interaction or authentication. An unauthenticated attacker can crash affected applications over the network, and public exploit code exists for this vulnerability. Currently no patch is available for remediation.
A vulnerability has been identified in SIMATIC ET 200AL IM 157-1 PN (6ES7157-1AB00-0AB0) (All versions), SIMATIC ET 200MP IM 155-5 PN HF (6ES7155-5AA00-0AC0) (All versions >= V4.2.0), SIMATIC ET 200SP IM 155-6 MF HF (6ES7155-6MU00-0CN0) (All versions), SIMATIC ET 200SP IM 155-6 PN HA (incl. [CVSS 7.5 HIGH]
RIOT OS ethos utility has a stack buffer overflow in _handle_char() due to missing bounds checking on serial frame data. Incoming frame bytes overflow a fixed-size stack buffer.
RIOT OS (IoT operating system) tapslip6 utility has a stack buffer overflow due to unbounded strcpy/strcat with user-controlled device name input. PoC available.
TinyOS versions up to and including 2.1.2 contain a stack-based buffer overflow vulnerability in the mcp2200gpio utility. The vulnerability is caused by unsafe use of strcpy() and strcat() functions when constructing device paths during automatic device discovery.
Ollama 0.11.5-rc0 through current version 0.13.5 contain a null pointer dereference vulnerability in the multi-modal model image processing functionality. [CVSS 7.5 HIGH]
LangChain versions up to and including 0.3.1 contain a regular expression denial-of-service (ReDoS) vulnerability in the MRKLOutputParser.parse() method (libs/langchain/langchain/agents/mrkl/output_parser.py). [CVSS 7.5 HIGH]
LlamaIndex (run-llama/llama_index) versions up to and including 0.12.2 contain an uncontrolled resource consumption vulnerability in the VannaPack VannaQueryEngine implementation. [CVSS 7.5 HIGH]
cpp-httplib versions prior to 0.30.1 are vulnerable to denial of service attacks due to insufficient validation of decompressed HTTP request body sizes. An unauthenticated remote attacker can send a malicious gzip or brotli-compressed request that decompresses to an arbitrarily large payload in memory, exhausting server resources. Public exploit code exists for this vulnerability, and a patch is available in version 0.30.1 and later.
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, avahi-daemon can be crashed by sending 2 unsolicited announcements with CNAME resource records 2 seconds apart. [CVSS 6.5 MEDIUM]
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, avahi-daemon can be crashed by sending unsolicited announcements containing CNAME resource records pointing it to resource records with short TTLs. [CVSS 6.5 MEDIUM]
Avahi is a system which facilitates service discovery on a local network via the mDNS/DNS-SD protocol suite. In 0.9-rc2 and earlier, an unprivileged local users can crash avahi-daemon (with wide-area disabled) by creating record browsers with the AVAHI_LOOKUP_USE_WIDE_AREA flag set via D-Bus. [CVSS 5.5 MEDIUM]
Xz-G12 Firmware versions up to 2.1.17 contains a vulnerability that allows attackers to undetected intrusions or failure to trigger safety alerts (CVSS 6.5).
Vllm versions up to 0.12.0 is affected by allocation of resources without limits or throttling (CVSS 6.5).
Python's filelock SoftFileLock implementation prior to version 3.20.3 contains a TOCTOU race condition that allows local attackers with symlink creation privileges to interfere with lock file operations between permission validation and file creation. An attacker can exploit this window to create a symlink at the target lock path, causing lock operations to fail or redirect to unintended files, resulting in denial of service or unexpected behavior. Upgrade to filelock version 3.20.3 or later to remediate this vulnerability.
RustCrypto's SM2 elliptic curve implementation in versions 0.14.0-pre.0 and 0.14.0-rc.0 is vulnerable to denial-of-service through improper input validation in the decrypt() function, allowing remote attackers to crash affected applications by submitting malformed or undersized ciphertext that triggers unhandled panics. Public exploit code exists for this vulnerability, though a patch is available.
XWiki Full Calendar Macro (before 2.4.5) has SQL injection accessible to guest users via the Calendar.JSONService page. Maximum CVSS 10.0 with scope change. Patch available.
CryptoLib versions prior to 1.4.3 contain a heap buffer overflow in the KMC crypto service's Base64 decoder, where oversized input strings can write beyond allocated buffer boundaries when processing KMC JSON responses. An attacker with network access to the KMC service can trigger this vulnerability to crash the spacecraft-ground station communication process or potentially execute arbitrary code. Public exploit code exists for this vulnerability, and no patch is currently available.
CryptoLib provides a software-only solution using the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) to secure communications between a spacecraft running the core Flight System (cFS) and a ground station. [CVSS 3.7 LOW]
CryptoLib versions prior to 1.4.3 leak approximately 400 bytes of memory with each call to the cryptography_encrypt() function due to unfreed buffers, allowing remote attackers to conduct denial-of-service attacks against spacecraft-to-ground communications by exhausting available memory through sustained traffic. Public exploit code exists for this vulnerability. The issue is resolved in version 1.4.3 and later.
CryptoLib versions prior to 1.4.3 contain an out-of-bounds read vulnerability in the base64urlDecode function that dereferences memory before validating input parameters, potentially causing a denial of service in spacecraft communications secured by SDLS-EP. Affected systems running cFS with vulnerable CryptoLib versions could crash when processing malformed base64 input. Public exploit code exists for this vulnerability, though no patch is currently available.
Vida V1 Pro Firmware versions up to 2.0.7 is affected by uncontrolled resource consumption (CVSS 7.5).
Data Domain Operating System versions up to 8.4.0.0 is affected by heap-based buffer overflow (CVSS 2.3).
Vivotek IP7137 camera ships without any admin password by default, and users are not informed they should set one. End-of-life product with no expected fix – all deployed cameras are likely exposed.
Gitlab versions up to 18.5.5 is affected by allocation of resources without limits or throttling (CVSS 6.5).
A flaw was found in GNU Wget2. This vulnerability, a stack-based buffer overflow, occurs in the filename sanitization logic when processing attacker-controlled URL paths, particularly when filename restriction options are active. [CVSS 7.6 HIGH]
Panda Wireless PWRU0 devices (firmware 2.2.9) expose WAN, LAN, and wireless configuration endpoints without authentication. Remote attackers can modify all network settings. PoC available.
Plesk Obsidian versions 8.0.1 through 18.0.73 are vulnerable to a Denial of Service (DoS) condition. [CVSS 7.5 HIGH]
An issue in Insiders Technologies GmbH e-invoice pro before release 1 Service Pack 2 allows a remote attacker to cause a denial of service via a crafted script [CVSS 7.5 HIGH]
An issue in Technitium DNS Server v.13.5 allows a remote attacker to cause a denial of service via the rate-limiting component [CVSS 7.5 HIGH]
CoreDNS is a DNS server that chains plugins. Prior to version 1.14.0, multiple CoreDNS server implementations (gRPC, HTTPS, and HTTP/3) lack critical resource-limiting controls. An unauthenticated remote attacker can exhaust memory and degrade or crash the server by opening many concurrent connections, streams, or sending oversized request bodies. The issue is similar in nature to CVE-2025-47950 (QUIC DoS) but affects additional server types that do not enforce connection limits, stream limit...
SQL injection in Parsl's visualization dashboard allows unauthenticated attackers to execute arbitrary database queries through unsafe string formatting of the workflow_id parameter. Public exploit code exists for this vulnerability, enabling potential data theft or database denial of service attacks against the monitoring infrastructure. The issue affects Parsl versions prior to 2026.01.05, which includes the fix.
Libsoup's NTLM authentication handler crashes when processing exceptionally long passwords due to a signed integer overflow in memory allocation calculations, affecting GNOME and applications relying on this library for network operations. An unauthenticated remote attacker can trigger a denial-of-service condition by sending specially crafted authentication requests. No patch is currently available.
Flagforge versions 2.3.2 and earlier suffer from a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint that accepts unvalidated usernames containing regex metacharacters, allowing unauthenticated remote attackers to trigger excessive CPU consumption and deny service to legitimate users. The MongoDB regex engine processes these malicious patterns inefficiently, making the platform unavailable without administrator intervention. No patch is currently available; users should implement WAF rules to filter regex metacharacters from username inputs as a temporary mitigation.
Llama.cpp server endpoints fail to validate the n_discard parameter from JSON input, allowing negative values that trigger out-of-bounds memory writes when the context buffer fills. This memory corruption vulnerability affects LLM inference operations and can be exploited remotely without authentication to crash the service or achieve code execution; public exploit code exists and no patch is currently available.
Panda3D egg-mkfont (through 1.10.16) has a stack buffer overflow via an unbounded sprintf() with attacker-controlled glyph pattern input. PoC available.
Panda3D's deploy-stub executable up to version 1.10.16 is vulnerable to denial of service through unvalidated stack allocation based on command-line argument counts, allowing local attackers to crash the application by supplying excessive arguments. Public exploit code exists for this vulnerability, and no patch is currently available. The flaw can trigger reliable crashes and undefined behavior during Python interpreter initialization.
Unsafe deserialization in Bio-Formats up to version 8.3.0 allows local attackers to execute arbitrary code or cause denial of service by crafting malicious .bfmemo cache files that are automatically loaded during image processing without validation. The Memoizer class deserializes untrusted data from these files, enabling potential remote code execution if suitable Java gadget chains are available on the classpath. No patch is currently available for this vulnerability (CVSS 7.8).
Bio-Formats versions up to 8.3.0 contain an XML External Entity (XXE) injection vulnerability in the Leica Microsystems metadata parser that fails to disable external entity expansion. A local attacker can exploit this by crafting malicious XML metadata files to trigger server-side request forgery, read local files, or cause denial of service. No patch is currently available.
OpenLDAP Lightning Memory-Mapped Database (LMDB) versions up to and including 0.9.14, prior to commit 8e1fda8, contain a heap buffer underflow in the readline() function of mdb_load.
RustFS is a distributed object storage system built in Rust. [CVSS 4.0 MEDIUM]
iccDEV versions prior to 2.3.1.2 are susceptible to denial of service through a null pointer dereference in the CIccProfileXml::ParseBasic() function, which can be triggered by local users with minimal privileges through user interaction. Public exploit code exists for this vulnerability, allowing attackers to crash the application and disrupt ICC color profile processing. A patch is available in version 2.3.1.2 and should be applied to affected systems.
processing of DCE/RPC requests contains a vulnerability that allows attackers to unexpectedly restart the Snort 3 Detection Engine, which could cause a denial of (CVSS 5.8).
An attacker with access to the system's internal network can cause a denial of service on the system by making two concurrent connections through the Telnet service.
The massive sending of ICMP requests causes a denial of service on one of the boards from the EVCharger that allows control the EV interfaces. Since the board must be operating correctly for the charger to also function correctly.
In Aris v10.0.23.0.3587512 and before, the file upload functionality does not enforce any rate limiting or throttling, allowing users to upload files at an unrestricted rate. [CVSS 6.5 MEDIUM]
The massive sending of ARP requests causes a denial of service on one board of the charger that allows control of the EV interfaces. Since the board must be operating correctly for the charger to also function correctly.
Transient DOS while parsing a WLAN management frame with a Vendor Specific Information Element. [CVSS 6.5 MEDIUM]
Transient DOS while parsing video packets received from the video firmware. [CVSS 5.5 MEDIUM]
AuntyFey Smart Combination Lock firmware versions as of 2025-12-24 contain a vulnerability that allows an unauthenticated attacker within Bluetooth Low Energy (BLE) range to cause a denial of service by repeatedly initiating BLE connections.
Aerohive HiveOS contains a denial of service vulnerability in the NetConfig UI that allows unauthenticated attackers to render the web interface unusable. Attackers can send a crafted HTTP request to the action.php5 script with specific parameters to trigger a 5-minute service disruption. [CVSS 7.5 HIGH]
iccDEV provides a set of libraries and tools for working with ICC color management profiles. Versions 2.3.1 and below contain a memory leak vulnerability in its XML MPE Parsing Path (iccFromXml). [CVSS 3.3 LOW]
In Modem, there is a possible system crash due to improper input validation. This could lead to remote denial of service, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. [CVSS 6.5 MEDIUM]
In Modem, there is a possible system crash due to incorrect error handling. This could lead to remote denial of service, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. [CVSS 6.5 MEDIUM]