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 (36873)
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.
Denial of service in Siemens SIMATIC ET 200 family PROFINET interface modules and PN/PN couplers allows remote unauthenticated attackers to render industrial controllers unresponsive by sending a single malformed S7 protocol Disconnect Request to TCP/102. The CVSS 4.0 score of 8.7 reflects the network-reachable, no-privileges-required vector against availability-critical OT assets, though EPSS is only 0.02% and no public exploit has been identified at time of analysis. Recovery requires a physical power cycle, which is operationally severe in plant environments.
Denial of service in Ollama's multi-modal image processing (versions 0.11.5-rc0 through 0.13.5) lets remote attackers crash the model runner by POSTing crafted base64 image data to the /api/chat endpoint. The decoded data is passed to mtmd_helper_bitmap_init_from_buf without validating that it is valid media; the function returns NULL on malformed input and the unchecked pointer is dereferenced, triggering a segmentation fault that takes the model offline for all users until restart. Rated CVSS 4.0 8.7 (availability-only impact); publicly available exploit code exists via a Huntr bounty, but EPSS is low (0.09%, 25th percentile) and it is not on CISA KEV.
Denial-of-service in LangChain versions up to and including 0.3.1 lets remote attackers exhaust CPU by feeding a crafted string into the MRKLOutputParser.parse() method, whose backtracking-prone regular expression exhibits catastrophic backtracking (ReDoS). Because MRKL agents parse LLM output to extract tool actions, an attacker who can influence that text - typically via prompt injection in downstream applications - can stall or hang the parsing thread. Publicly available exploit code exists (huntr bounty), though EPSS is low at 0.08% and it is not on the CISA KEV list.
Denial-of-service in LlamaIndex (run-llama/llama_index) versions up to and including 0.12.2 lets remote unauthenticated attackers exhaust CPU and memory through the VannaPack VannaQueryEngine. The engine's custom_query() converts a user-supplied natural-language prompt into SQL and runs it via vn.run_sql() with no execution limits, so a crafted prompt can produce an unbounded or extremely expensive query. Publicly available exploit code exists (Huntr bounty report), though EPSS is low at 0.12% (30th percentile) and it is not listed in CISA KEV.
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]
A security flaw has been discovered in lief-project LIEF up to 0.17.1. Affected by this issue is the function Parser::parse_binary of the file src/ELF/Parser.tcc of the component ELF Binary Parser. [CVSS 3.3 LOW]
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.
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'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]
In display, there is a possible memory corruption due to use after free. This could lead to local escalation of privilege if a malicious actor has already obtained the System privilege. [CVSS 6.7 MEDIUM]
In display, there is a possible memory corruption due to use after free. This could lead to local escalation of privilege if a malicious actor has already obtained the System privilege. [CVSS 7.8 HIGH]
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]
Nr15 versions up to - is affected by improper check for unusual or exceptional conditions (CVSS 6.5).
In Modem, there is a possible read of uninitialized heap data due to an uncaught exception. 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]
iccDEV ICC color profile processing library versions 2.3.1 and below contain an infinite loop in the CalcProfileID function that allows unauthenticated remote attackers to cause denial of service. Public exploit code exists for this vulnerability, and affected systems should upgrade to version 2.3.1.1 or later to remediate the issue.
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. In versions 3.13.2 and below, handling of chunked messages can result in excessive blocking CPU usage when receiving a large number of chunks. [CVSS 5.3 MEDIUM]
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Versions 3.13.2 and below allow for an infinite loop to occur when assert statements are bypassed, resulting in a DoS attack when processing a POST body. [CVSS 7.5 HIGH]
Denial of service in Anthropic's Model Context Protocol (MCP) TypeScript SDK versions up to and including 1.25.1 allows remote attackers to hang the Node.js event loop by submitting a crafted URI to the UriTemplate matcher. The dynamically built regex for RFC 6570 exploded array patterns contains nested quantifiers that trigger catastrophic backtracking, pinning CPU and rendering the process unresponsive. Publicly available exploit code exists, though EPSS is very low (0.02%) and it is not listed in CISA KEV, so real-world exploitation currently appears theoretical rather than widespread.
Coolify is an open-source and self-hostable tool for managing servers, applications, and databases. In Coolify vstarting with version 4.0.0-beta.434, the /login endpoint advertises a rate limit of 5 requests but can be trivially bypassed by rotating the X-Forwarded-For header. [CVSS 4.3 MEDIUM]
Evershop contains a vulnerability that allows attackers to exhaust the application server's resources via the "GET /images" API (CVSS 7.5).
An issue was discovered in the Camera in Samsung Mobile Processor and Wearable Processor Exynos 1330, 1380, 1480, 2400, 1580, 2500. A race condition in the issimian device driver results in a double free, leading to a denial of service. [CVSS 5.9 MEDIUM]
An issue was discovered in the Camera in Samsung Mobile Processor and Wearable Processor Exynos 1330, 1380, 1480, 2400, 1580, 2500. An invalid kernel address dereference in the issimian device driver leads to a denial of service. [CVSS 6.2 MEDIUM]
An issue was discovered in the Camera in Samsung Mobile Processor and Wearable Processor Exynos 1330, 1380, 1480, 2400, 1580, 2500. A race condition in the issimian device driver results in an out-of-bounds access, leading to a denial of service. [CVSS 5.1 MEDIUM]
An issue was discovered in L2 in Samsung Mobile Processor, Wearable Processor, and Modem Exynos 980, 990, 850, 1080, 2400, 1580, 9110, W920, W930, Modem 5123, and Modem 5400. Incorrect handling of RRC packets leads to a Denial of Service. [CVSS 7.5 HIGH]
An issue was discovered in the Camera in Samsung Mobile Processor and Wearable Processor Exynos 1330, 1380, 1480, 2400, 1580, and 2500. Improper validation of user-space input in the issimian device driver leads to information disclosure and a denial of service. [CVSS 7.1 HIGH]
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.
Rejected reason: This CVE ID was rejected because it was reserved but not used for a vulnerability disclosure. No vendor patch available.