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 (39999)
Tenda AX-1806 v1.0.0.1 was discovered to contain a stack overflow in the deviceList parameter of the formSetWifiMacFilterCfg function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
A null pointer dereference in the Linux kernel's socket error queue handling causes a denial of service when CONFIG_HARDENED_USERCOPY is enabled and applications attempt to retrieve error messages via recvmsg(). Local attackers with user privileges can trigger a kernel panic by reading from the socket error queue on affected systems running vulnerable kernel versions.
A flaw was found in glib. Missing validation of offset and count parameters in the g_buffered_input_stream_peek() function can lead to an integer overflow during length calculation. [CVSS 3.7 LOW]
M-Files Server before version 26.1.15632.3 can be crashed by authenticated administrators with vault privileges through an unsafe API endpoint, resulting in service disruption. This denial-of-service vulnerability requires high-level privileges and network access, making it a limited-scope threat to organizations running vulnerable versions. No patch is currently available.
A null pointer dereference in the Linux kernel's QFQ packet scheduler (net/sched/sch_qfq) allows local attackers with user privileges to cause a denial of service by deactivating an inactive aggregate during qdisc reset operations. The vulnerability occurs when multiple QFQ qdisc instances share a leaf qdisc, causing incorrect state assumptions during cleanup. A patch is available to resolve this issue.
Vulnerability in the Oracle VM VirtualBox product of Oracle Virtualization (component: Core). Supported versions that are affected are 7.1.14 and 7.2.4. [CVSS 4.6 MEDIUM]
Vulnerability in the Java VM component of Oracle Database Server. Supported versions that are affected are 19.3-19.29 and 21.3-21.20. [CVSS 4.5 MEDIUM]
Mysql Server contains a vulnerability that allows attackers to unauthorized ability to cause a hang or frequently repeatable crash (complete DO (CVSS 6.5).
Mysql Server contains a vulnerability that allows attackers to unauthorized ability to cause a partial denial of service (partial DOS) of MySQL (CVSS 2.7).
Mysql contains a vulnerability that allows attackers to unauthorized ability to cause a hang or frequently repeatable crash (complete DO (CVSS 4.9).
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Parser). Supported versions that are affected are 9.0.0-9.5.0. [CVSS 4.9 MEDIUM]
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 9.0.0-9.5.0. [CVSS 6.5 MEDIUM]
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 9.0.0-9.5.0. [CVSS 6.5 MEDIUM]
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.0-8.0.44, 8.4.0-8.4.7 and 9.0.0-9.5.0. [CVSS 4.9 MEDIUM]
Vulnerability in the Oracle Solaris product of Oracle Systems (component: Filesystems). Supported versions that are affected are 10 and 11. [CVSS 5.0 MEDIUM]
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.0-8.0.44, 8.4.0-8.4.7 and 9.0.0-9.5.0. [CVSS 4.9 MEDIUM]
Mysql Server contains a vulnerability that allows attackers to unauthorized ability to cause a hang or frequently repeatable crash (complete DO (CVSS 4.9).
Mysql Cluster contains a vulnerability that allows attackers to unauthorized ability to cause a hang or frequently repeatable crash (complete DO (CVSS 4.9).
Mysql Server contains a vulnerability that allows attackers to unauthorized ability to cause a hang or frequently repeatable crash (complete DO (CVSS 5.3).
A buffer over-read in the PublicKey::verify() method of Binance - Trust Wallet Core before commit 5668c67 allows attackers to cause a Denial of Service (DoS) via a crafted input. [CVSS 7.5 HIGH]
A NULL pointer dereference in the dacp_reply_playqueueedit_move function (src/httpd_dacp.c) of owntone-server commit b7e385f allows attackers to cause a Denial of Service (DoS) via sending a crafted DACP request to the server. [CVSS 7.5 HIGH]
A NULL pointer dereference in the parse_meta function (src/httpd_daap.c) of owntone-server commit 334beb allows attackers to cause a Denial of Service (DoS) via sending a crafted DAAP request to the server. [CVSS 7.5 HIGH]
We have identified a bug in Node.js error handling where "Maximum call stack size exceeded" errors become uncatchable when `async_hooks.createHook()` is enabled. Instead of reaching `process.on('uncaughtException')`, the process terminates, making the crash unrecoverable. [CVSS 7.5 HIGH]
A malformed `HTTP/2 HEADERS` frame with oversized, invalid `HPACK` data can cause Node.js to crash by triggering an unhandled `TLSSocket` error `ECONNRESET`. Instead of safely closing the connection, the process crashes, enabling a remote denial of service. [CVSS 7.5 HIGH]
A memory leak in Node.js’s OpenSSL integration occurs when converting `X.509` certificate fields to UTF-8 without freeing the allocated buffer. [CVSS 7.5 HIGH]
NULL pointer dereference in the dacp_reply_playqueueedit_clear function in src/httpd_dacp.c in owntone-server through commit 6d604a1 (newer commit after version 28.12) allows remote attackers to cause a Denial of Service (crash). [CVSS 7.5 HIGH]
NULL pointer dereference in the daap_reply_groups function in src/httpd_daap.c in owntone-server through commit 5e6f19a (newer commit after version 28.2) allows remote attackers to cause a Denial of Service. [CVSS 7.5 HIGH]
NVIDIA Nsight Systems for Windows contains a vulnerability in the application’s DLL loading mechanism where an attacker could cause an uncontrolled search path element by exploiting insecure DLL search paths. [CVSS 6.7 MEDIUM]
NVIDIA Nsight Systems for Linux contains a vulnerability in the .run installer, where an attacker could cause an OS command injection by supplying a malicious string to the installation path. [CVSS 7.3 HIGH]
NVIDIA Nsight Visual Studio for Windows contains a vulnerability in Nsight Monitor where an attacker can execute arbitrary code with the same privileges as the NVIDIA Nsight Visual Studio Edition Monitor application. [CVSS 7.3 HIGH]
NVIDIA Nsight Systems contains a vulnerability in the gfx_hotspot recipe, where an attacker could cause an OS command injection by supplying a malicious string to the process_nsys_rep_cli.py script if the script is invoked manually. [CVSS 7.3 HIGH]
In tinyMQTT commit 6226ade15bd4f97be2d196352e64dd10937c1962 (2024-02-18), a memory leak occurs due to the broker's failure to validate or reject malformed UTF-8 strings in topic filters. [CVSS 7.5 HIGH]
A security issue exists within ArmorStart® LT that can result in a denial-of-service condition. This vulnerability is triggered during fuzzing of multiple CIP classes, which causes the CIP port to become unresponsive. [CVSS 7.5 HIGH]
A security issue exists within ArmorStart® LT that can result in a denial-of-service condition. During execution of the Achilles Comprehensive step limit storm tests, the device reboots [CVSS 7.5 HIGH]
A security issue exists within ArmorStart® LT that can result in a denial-of-service condition. After running a Burp Suite active scan, the device loses ICMP connectivity, causing the web application to become inaccessible. [CVSS 7.5 HIGH]
Multiple denial-of-service vulnerabilities exist in the affected product. These issues can be triggered through various crafted inputs, including malformed Class 3 messages, memory leak conditions, and other resource exhaustion scenarios.
affected product. The security issue occurs when a malformed CIP forward open message is sent. This contains a vulnerability that allows attackers to a major nonrecoverable fault a restart is required to recover.
dr_flac, an audio decoder within the dr_libs toolset, contains an integer overflow vulnerability flaw due to trusting the totalPCMFrameCount field from FLAC metadata before calculating buffer size, allowing an attacker with a specially crafted file to perform DoS against programs using the tool. [CVSS 5.5 MEDIUM]
Swift W3C TraceContext and Swift OTel improperly validate malformed HTTP headers, enabling remote attackers to crash affected services through denial-of-service attacks. This vulnerability affects applications using these libraries for distributed tracing and telemetry, particularly HTTP servers processing untrusted network input. No patch is currently available, though versions 1.0.0-beta.5 of Swift W3C TraceContext and 1.0.4 of Swift OTel are expected to address the issue.
Mytube versions up to 1.7.71 contains a vulnerability that allows attackers to bypass IP-based rate limiting on general API endpoints (CVSS 6.5).
Birkir Prime versions up to 0.4.0.beta.0 are vulnerable to resource exhaustion attacks through the GraphQL Alias Handler endpoint, allowing unauthenticated remote attackers to cause denial of service. Public exploit code is available for this vulnerability, and the project has not yet released a patch despite early notification. The attack requires no user interaction and can be executed over the network with minimal complexity.
Prime versions up to 0.4.0.beta.0 are vulnerable to denial of service attacks through the GraphQL Array Based Query Batch Handler component, which can be exploited remotely without authentication. Public exploit code exists for this vulnerability, and the vendor has not yet released a patch despite early notification.
Wings is the server control plane for Pterodactyl, a free, open-source game server management panel. Prior to version 1.12.0, websockets within wings lack proper rate limiting and throttling. [CVSS 6.5 MEDIUM]
Birkir Prime versions up to 0.4.0.beta.0 contain a denial of service vulnerability in the GraphQL Directive Handler that can be exploited remotely without authentication. Public exploit code exists for this vulnerability, and the developers have not released a patch despite early notification. An unauthenticated attacker can leverage this flaw to disrupt service availability.
Remote denial of service in birkir Prime up to version 0.4.0.beta.0 can be triggered through the GraphQL Field Handler endpoint without authentication. Public exploit code exists for this vulnerability, though no patch is currently available from the project maintainers.
Pterodactyl is a free, open-source game server management panel. Pterodactyl implements rate limits that are applied to the total number of resources (e.g. [CVSS 6.5 MEDIUM]
Quicly, an IETF QUIC protocol implementation, is susceptible to a denial-of-service attack prior to commit d9d3df6a8530a102b57d840e39b0311ce5c9e14e. A remote attacker can exploit these bugs to trigger an assertion failure that crashes process using Quicly. [CVSS 7.5 HIGH]
Use-after-free in QuickJS up to version 0.11.0 within the Atomics Ops Handler allows remote attackers to trigger memory corruption without authentication. Public exploit code exists for this vulnerability, enabling potential information disclosure or denial of service. A patch is available and should be applied immediately.
A vulnerability was determined in Open5GS up to 2.7.6. Impacted is the function sgwc_s11_handle_downlink_data_notification_ack of the file src/sgwc/s11-handler.c of the component sgwc. [CVSS 5.3 MEDIUM]
A security vulnerability has been detected in Open Asset Import Library Assimp up to 6.0.2. Affected by this vulnerability is the function Assimp::LWOImporter::FindUVChannels of the file /src/assimp/code/AssetLib/LWO/LWOMaterial.cpp. [CVSS 5.3 MEDIUM]
A security flaw has been discovered in nicbarker clay versions up to 0.14. is affected by improper resource shutdown or release (CVSS 3.3).
A security flaw has been discovered in Open5GS up to 2.7.5. This issue affects some unknown processing of the component Timer Handler. [CVSS 5.3 MEDIUM]
A vulnerability was identified in Open5GS up to 2.7.5. This vulnerability affects the function sgwc_bearer_add of the file src/sgwc/context.c. [CVSS 5.3 MEDIUM]
A vulnerability was determined in Open5GS up to 2.7.6. This affects the function sgwc_s11_handle_create_indirect_data_forwarding_tunnel_request of the file /src/sgwc/s11-handler.c. [CVSS 5.3 MEDIUM]
A vulnerability was found in Open5GS up to 2.7.6. Affected by this issue is the function sgwc_s5c_handle_create_session_response of the file src/sgwc/s5c-handler.c. [CVSS 5.3 MEDIUM]
A vulnerability has been found in Open5GS up to 2.7.6. Affected by this vulnerability is an unknown functionality of the component GTPv2 Bearer Response Handler. [CVSS 5.3 MEDIUM]
Sandboxie 5.49.7 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the container folder input field. Attackers can paste a large buffer of repeated characters into the Sandbox container folder setting to trigger an application crash. [CVSS 7.5 HIGH]
mashREPL tool contains a vulnerability that allows attackers to crash the application by pasting malformed input (CVSS 7.5).
iDailyDiary 4.30 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the preferences tab name field. Attackers can paste a 2,000,000 character buffer into the default diary tab name to trigger an application crash. [CVSS 7.5 HIGH]
RarmaRadio 2.72.8 contains a denial of service vulnerability that allows attackers to crash the application by overflowing network configuration fields with large character buffers. [CVSS 7.5 HIGH]
DupTerminator 1.4.5639.37199 contains a denial of service vulnerability that allows attackers to crash the application by inputting a long character string in the Excluded text box. Attackers can generate a payload of 8000 repeated characters to trigger the application to stop working on Windows 10. [CVSS 7.5 HIGH]
mmstu.c in VideoLAN VLC media player versions up to 3.0.22 is affected by out-of-bounds read (CVSS 4.8).
In MIT Kerberos 5 (aka krb5) before 1.22 (with incremental propagation), there is an integer overflow for a large update size to resize() in kdb_log.c. An authenticated attacker can cause an out-of-bounds write and kadmind daemon crash. [CVSS 7.1 HIGH]
Tenda AX-1806 v1.0.0.1 was discovered to contain a stack overflow in the security parameter of the sub_4C408 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 timeZone parameter of the fromSetSysTime function. This vulnerability allows attackers to cause a Denial of Service (DoS) via a crafted request. [CVSS 7.5 HIGH]
Mattermost versions 10.11.x <= 10.11.8, 11.1.x <= 11.1.1, 11.0.x <= 11.0.6 fail to prevent infinite re-renders on API errors which allows authenticated users to cause application-level DoS via triggering unbounded component re-render loops. [CVSS 6.8 MEDIUM]
Nsauditor 3.2.3 contains a denial of service vulnerability in the registration code input field that allows attackers to crash the application. Attackers can paste a large buffer of 256 repeated characters into the 'Key' field to trigger an application crash. [CVSS 7.5 HIGH]
NBMonitor 1.6.8 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the registration code input field. Attackers can paste a 256-character buffer into the registration key field to trigger an application crash and potential system instability. [CVSS 7.5 HIGH]
Backup Key Recovery 2.2.7 contains a denial of service vulnerability that allows attackers to crash the application by overflowing the registration code input field. [CVSS 7.5 HIGH]
NoteBurner 2.35 contains a buffer overflow in the license code input field that enables local attackers to crash the application or potentially execute arbitrary code by supplying an oversized activation key.
Leawo Prof. Media 11.0.0.1 contains a denial of service vulnerability that allows attackers to crash the application by supplying an oversized payload in the activation keycode field. [CVSS 7.5 HIGH]
Telegram Desktop versions up to 2.9.2 is affected by allocation of resources without limits or throttling (CVSS 7.5).
Smartftp versions up to 10.0.2909.0 is affected by allocation of resources without limits or throttling (CVSS 7.5).
Yenkee Hornet Gaming Mouse driver GM312Fltr.sys contains a buffer overrun vulnerability that allows attackers to crash the system by sending oversized input. Attackers can exploit the driver by sending a 2000-byte buffer through DeviceIoControl to trigger a kernel-level system crash. [CVSS 7.5 HIGH]
Redragon Gaming Mouse driver contains a kernel-level vulnerability that allows attackers to trigger a denial of service by sending malformed IOCTL requests. Attackers can send a crafted 2000-byte buffer with specific byte patterns to the REDRAGON_MOUSE device to crash the kernel driver. [CVSS 7.5 HIGH]
Denial of service in Traefik versions prior to 2.11.35 and 3.6.7 allows unauthenticated remote attackers to exhaust server resources by establishing incomplete ACME TLS-ALPN connections and leaving them open indefinitely. An attacker can send minimal ClientHello messages with the acme-tls/1 protocol and cease responding, causing goroutines and file descriptors to be held until the entry point becomes unavailable. The vulnerability affects systems with ACME TLS challenge enabled.
Repeated telemetry collector subscriptions in Juniper Junos OS and Junos OS Evolved trigger a use-after-free vulnerability in the chassis daemon, allowing authenticated network attackers to crash critical processes and cause denial of service. Affected versions prior to 22.4R3-S8, 23.2R2-S5, and 23.4R2 are vulnerable when telemetry-capable daemons experience continuous sensor subscription cycles. No patch is currently available, leaving affected systems exposed until updates are released.
A race condition in Juniper Junos OS on MX10k Series with LC480 or LC2101 line cards allows low-privileged local users to crash line card and potentially chassis daemons by repeatedly executing the 'show system firmware' command. Affected versions include all releases before 21.2R3-S10 and multiple later branches up to 23.2R, with no patch currently available. This denial of service vulnerability requires local access and can be triggered without elevated privileges.
EVPN-VXLAN traffic interruption in Juniper Junos on EX4k and QFX5k Series platforms allows adjacent network attackers to trigger interface link flaps that cause inter-VNI traffic to drop in configurations using Virtual Port-Link Aggregation Groups. An unauthenticated attacker can exploit this condition to deny service to VXLAN traffic between virtual network identifiers when multiple load-balanced next-hop routes exist for the same destination. No patch is currently available for this vulnerability.
Denial of service in Juniper Junos OS and Junos OS Evolved allows an adjacent IS-IS neighbor to trigger a memory leak in the routing protocol daemon by sending specially crafted update packets. Repeated exploitation exhausts available memory and crashes the rpd process, rendering routing unavailable. No patch is currently available.
Denial-of-service in Juniper Junos OS Packet Forwarding Engine allows authenticated attackers to crash Forwarding Processor Cards by subscribing to telemetry sensors at scale, forcing service restarts and network disruption. The vulnerability affects Junos versions before 22.4R3-S7, 23.2R2-S4, and 23.4R2, with no patch currently available. Installation of specific YANG sensor packages mitigates the issue.
Juniper Junos OS Forwarding Plane Crash (FPC) denial of service occurs when a network-adjacent attacker sends a specially crafted ICMPv4 packet with a malformed IP header, causing the affected line card to crash and restart. The attack is limited to directly adjacent networks since upstream routers filter such malformed packets before forwarding. No patch is currently available for this vulnerability affecting multiple Junos OS versions.
A NULL Pointer Dereference vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS on MX, SRX and EX Series allows a local attacker with low privileges to cause a Denial-of-Service (DoS). [CVSS 5.5 MEDIUM]
A Buffer Over-read vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). [CVSS 7.5 HIGH]
An Improper Check for Unusual or Exceptional Conditions vulnerability in the Juniper DHCP service (jdhcpd) of Juniper Networks Junos OS and Junos OS Evolved allows a DHCP client in one subnet to exhaust the address pools of other subnets, leading to a Denial of Service (DoS) on the downstream DHCP server. By default, the DHCP relay agent inserts its own Option 82 information when forwarding client requests, optionally replacing any Option 82 information provided by the client. When a speci...
An Untrusted Pointer Dereference vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, authenticated attacker with low privileges to cause a Denial-of-Service (DoS). [CVSS 5.5 MEDIUM]
An issue in nanomq v0.22.7 allows attackers to cause a Denial of Service (DoS) via a crafted request. The number of data packets received in the recv-q queue of the Nanomq process continues to increase, causing the nanomq broker to fall into a deadlock and be unable to provide normal services. [CVSS 7.5 HIGH]
A heap overflow in the uncv_parse_config() function of GPAC v2.4.0 allows attackers to cause a Denial of Service (DoS) via a crafted MP4 file. [CVSS 5.5 MEDIUM]
A heap overflow in the ghi_dmx_declare_opid_bin() function of GPAC v2.4.0 allows attackers to cause a Denial of Service (DoS) via a crafted input. [CVSS 5.5 MEDIUM]
SvelteKit 2.19.0-2.49.4 has SSRF/DoS affecting applications with prerendered routes. Can be exploited to make the server perform arbitrary requests or become unresponsive. Patch available.