Inefficient Regular Expression Complexity

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (Parser::parseBlock()) and inline (Inline::parseSequence() / Inline::parseMapping()) parsers to recurse without a depth limit. A crafted document exhausts the PHP stack and crashes the worker. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.Show less

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. From 7.3.0-BETA1 until 7.4.12 and 8.0.12, the JsonPath component compiles attacker-controlled match() and search() filter patterns directly into preg_match() without a length cap, i-regexp restriction, or bounded backtracking, allowing catastrophic-backtracking expressions to pin worker CPU and cause denial of service. This issue is fixed in versions 7.4.12 and 8.0.12.Show less

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658Show less

Phalcon is a high-performance, full-stack PHP framework. Prior to 5.15.0, every Phalcon MVC application built with a default router registers a built-in route whose compiled PCRE pattern contains the nested quantifier (/.), and the same construct is produced by the /:params placeholder and the CLI router. Phalcon\Mvc\Router::handle() matches this pattern against the attacker-controlled request URI on every request, so a crafted path such as one containing repeated slashes followed by decoded newlines can trigger catastrophic backtracking and cause CPU exhaustion or route-matching failure. This issue is fixed in version 5.15.0.Show less

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.2 before 0.10.0, the SKILL_MENTION_RE and strip_re regular expressions in backend/open_webui/utils/middleware.py parsed <$skillId|label> skill mentions with overlapping quantifiers, allowing an authenticated chat message containing <$ without a closing > to trigger quadratic backtracking and block the asyncio event loop. This issue is fixed in version 0.10.0.Show less

HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.10, the fix for CVE-2026-45367 incompletely patched the DSTU2 module, leaving FHIRPathEngine.matches() in org.hl7.fhir.dstu2/utils/FHIRPathEngine.java to call raw String.matches(sw) without RegexTimeout protection while replaceMatches() was updated, allowing an unauthenticated attacker to trigger catastrophic regex backtracking and exhaust server CPU. This issue is fixed in version 6.9.10.Show less

A flaw was found in `guardrails-detectors`, a component of Red Hat OpenShift AI. This vulnerability, known as Regular Expression Denial of Service (ReDoS), allows a remote attacker to provide specially crafted regular expressions to the public detection API. This can cause catastrophic backtracking, leading to a worker process consuming 100% CPU indefinitely and resulting in a denial of service for the entire guardrails-mediated LLM pipeline.Show less

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.Show less

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.Show less

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.Show less

String::Util versions before 1.36 for Perl are susceptible to a regular expression denial of service. The trim and rtrim functions stripped trailing whitespace with s/\s*$//u. Because \s* matches greedily and the $ anchor fails whenever a non-whitespace character follows the whitespace, the regex engine retries the match at each offset of a long whitespace run, producing quadratic backtracking. The fix replaces \s*$ with \s+$. Any caller that passes untrusted input to trim or rtrim can trigger CPU exhaustion with a string containing a long run of whitespace.Show less

vLLM is a high-throughput and memory-efficient inference and serving engine for LLMs. Prior to 0.24.0, the structured_outputs.regex API parameter passes a user-supplied regular expression string directly to the grammar compiler backends with no compilation timeout; in the xgrammar backend the string reaches the regex compiler with no guard, and in the outlines backend the validation step blocks structural issues such as lookarounds and backreferences but performs no complexity analysis, so a pattern with nested quantifiers passes all checks and causes exponential state-space expansion, allowing a single request containing an adversarial regex to hang an inference worker indefinitely and deny service. This issue is fixed in version 0.24.0.Show less

LobeChat before version 2.2.10-canary.15 contains a regular expression denial of service (ReDoS) vulnerability that allows authenticated attackers to block the Node.js event loop by supplying a catastrophic-backtracking pattern in a GitHub repository URL path during skill import. Attackers can craft a malicious basePath value containing unescaped regex metacharacters such as catastrophic-backtracking patterns, which are injected into a dynamically constructed regular expression in the findSkillMd function and executed synchronously against archive entries, denying service to all concurrent users for tens of seconds per request.Show less

Sentry is an error tracking and performance monitoring tool. From 24.4.0 until 26.5.2, a Regular Expression Denial of Service (ReDoS) vulnerability exists in Sentry's event ingestion pipeline, where a regex applied to attacker-controlled fields on incoming events can be made to consume disproportionate CPU time. This vulnerability is fixed in 26.5.2.Show less

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.Show less

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 22.0.1, 21.2.17, and 20.3.25, a Denial of Service (DoS) vulnerability exists in the @angular/common package of the Angular framework. The formatDate function, which is also utilized by the standard Angular DatePipe, does not properly limit or validate the length of the format parameter. When parsing a maliciously crafted, excessively long date format string (e.g., a repeating pattern or very large string), the internal parser splits the string iteratively using a regular expression loop. This results in uncontrolled resource consumption (high CPU utilization and excessive memory allocations), leading to a Denial of Service (DoS). This vulnerability is fixed in 22.0.1, 21.2.17, and 20.3.25.Show less

vLLM versions >= 0.6.3 and < 0.9.0 contain multiple regular expression denial of service (ReDoS) vulnerabilities. Several regex patterns — in vllm/lora/utils.py, the phi4mini tool parser, and the OpenAI-compatible serving chat endpoint — are susceptible to catastrophic backtracking. An attacker submitting crafted input with nested or repeated structures can trigger severe CPU consumption and performance degradation, resulting in denial of service.Show less

js-toml is a TOML parser for JavaScript, fully compliant with the TOML 1.0.0 Spec. Versions up to and including 1.1.0 parse hexadecimal / octal / binary integer literals via a hand-written `parseBigInt` loop that multiplies a `BigInt` accumulator by the radix once per input digit. Each iteration performs a `BigInt * BigInt` operation on an accumulator that grows linearly with the number of digits already consumed, so the whole loop is O(n²) in the literal length. The lexer regex places no upper bound on the literal length, so a single TOML document containing one ~500 kB hex literal pins one CPU core for ~40 seconds on a modern laptop (Apple M-series, Node v22). Memory amplification is bounded but CPU amplification is severe and grows quadratically: doubling the literal length quadruples the work. A caller that invokes `load()` on attacker-controlled TOML (configuration upload endpoints, CI/CD systems ingesting third-party `*.toml`, IDE plugins, build tools) is exposed to a single-request CPU exhaustion DoS. Version 1.1.1 fixes the issue.Show less

LiquidJS is a Shopify/GitHub Pages compatible template engine written in pure JavaScript. In versions 10.25.7 and below, the built-in strip_html filter uses a regex containing four flawed lazy-quantified alternatives, leading to ReDoS via quadratic backtracking. When the input contains many <script, <style, or <!-- opener tokens without matching closers, the V8 regex engine performs O(N²) backtracking, blocking the Node.js event loop. A single ~350 KB request ('<script'.repeat(50000)) stalls the process for ~10 seconds; cost grows quadratically with input size. The default memoryLimit: Infinity does not bound regex CPU, and even when configured strip_html only charges str.length to the limit — the regex itself runs unbounded. A single unauthenticated request containing crafted untrusted input can cause severe event-loop blocking and CPU amplification that saturates Node.js workers while bypassing memoryLimit protections. This issue has been fixed in version 10.26.0.Show less

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.77 and 9.9.1-alpha.1, an unauthenticated attacker who knows a publicly-known Parse Application ID can submit a single HTTP request whose client SDK version field contains adversarial input that triggers polynomial backtracking in a request-header parser. The parsing runs before session authentication and before rate limiting on every /parse/* request, so the request consumes seconds to minutes of synchronous CPU on a Node.js worker before any access control evaluates it. A small number of concurrent requests can saturate a worker; a single large request via the body-field variant can pin a worker for minutes. Production deployments running the default configuration are affected. This issue has been patched in versions 8.6.77 and 9.9.1-alpha.1.Show less