Weakness (CWE)
CWE-1333: Inefficient Regular Expression Complexity
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
How to prevent it (4 mitigations)
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Architecture and Design
Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
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System Configuration
Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
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Implementation
Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
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Implementation
Limit the length of the input that the regular expression will process.
Source: MITRE CWE-1333
587 results · Feed
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Medium 5.3
vLLM: ReDoS via structured_outputs.regex in the lm-format-enforcer backend (no compile timeout) — missed sibling of CVE-2026-55574
vLLM is an inference and serving engine for large language models. Prior to 0.26.0, the structured_outputs.regex parameter in vllm/v1/structured_output/backend_lm_format_enforcer.py is passed to lmformatenforcer.RegexParser without compile_regex_with_timeout …
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High 7.5
crmne/ruby_llm at commit fa6f279847d6d7027814539d9c0dfc3bbdfd2a83 contains a polynomial-time regular expression denial-…
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Medium 4.3
CyberChef’s pretty-recipe parser vulnerable to client-side ReDoS / CPU exhaustion when parsing a malformed #recipe= URL
CyberChef is a web app for encryption, encoding, compression, and data analysis. Prior to 11.3.0, CyberChef's pretty-recipe parser in src/core/Utils.mjs can exhaust client-side CPU when a malformed #recipe= URL fragment containing a large number of unmatched …
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Medium 5.3
Hono: ReDoS in CORS middleware via Access-Control-Request-Headers
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.34, the built-in CORS middleware, hono/cors, is vulnerable to a regular expression denial of service (ReDoS). During a preflight OPTIONS request, the middlewar…
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Medium 5.3
SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit's request handling (for headers such as Accept) uses a regular expression vulnerable to …
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High 7.5
pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors
pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimite…
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High 8.2
Quadratic regex backtracking in the html_sanitize_ex CSS scrubber allows CPU-exhaustion denial of service
Inefficient Regular Expression Complexity vulnerability in the CSS scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to exhaust server CPU via a long CSS declaration in sanitized HTML. The declaration regex in HtmlSanitizeEx.Scrubb…
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High 8.7
In OpenStack Swift through 2.38.0, the proxy server Accept header parser contains a regular expression vulnerable to ca…
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Medium 6.5
Open WebUI: Any authenticated user can stall a worker via a knowledge-search pattern that backtracks catastrophically
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.6 until 0.11.0, the built-in knowledge search path in backend/open_webui/tools/knowledge_fs.py and backend/open_webui/tools/builtin.py let a chat participant choose…
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Medium 6.5
Open WebUI: Instance-wide stall via automation recurrence rules that force multi-second parsing
Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.0 until 0.11.0, automation recurrence parsing in backend/open_webui/utils/automations.py anchored minutely and hourly rules at a fixed date of 2000-01-01 and then w…
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High 8.2
Thumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypass via wildcard dot
Thumbor is an open-source photo thumbnail service by globo.com. Prior to 7.8.0, the ALLOWED_SOURCES configuration passes plain strings to re.match() without escaping dots, so a hostname differing at dot positions can match the allowlist. This issue is fixed i…
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High 7.5
Natural Language Toolkit (NLTK): ReDoS in NLTK ReviewsCorpusReader FEATURES regex
### Summary `ReviewsCorpusReader` extracts feature annotations of the form *label* followed by a bracketed signed digit (e.g. a label then `[+2]`) from each review line, using the module-level `FEATURES` regex. The feature-label sub-pattern is unbounded — an …
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Medium 5.3
Apache Superset: Regular Expression Denial of Service (ReDoS) in SQL Parser
A Regular Expression Denial of Service (ReDoS) vulnerability exists in Apache Superset versions 1.5.0 through 5.0.0. The vulnerability is located in the sql_parse.py component, specifically within the SQL_REGEX used for parsing SQL statements in the sqlparse …
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High 7.5
Date::Manip versions through 7.00 for Perl allow CPU exhaustion via quadratic backtracking in the unanchored time substitution in _parse_time
Date::Manip versions through 7.00 for Perl allow CPU exhaustion via quadratic backtracking in the unanchored time substitution in _parse_time. _parse_time removes a time from anywhere in the string with the unanchored substitution `s/$timerx/ /`, where $timer…
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Medium 6.9
ReDoS in Open Mercato
Open Mercato does not validate regex rules. An attacker with privileges to create the regex rule can add an unsafe regex to a field. When someone provide the proper string it can result in a DoS attack. This issue was fixed in version 0.6.4.
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High 7.5
HAPI FHIR: ReDoS via FHIRPath matches()/replaceMatches() in FHIR Validator HTTP Endpoint
HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.9 and 6.9.4.2, all implementations of FHIRPathEngine accept arbitrary FHIRPath expressions and evaluate them without input validation, and th…
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High 7.5
JSONata: Malicious inputs to "$toMillis" function can cause resource exhaustion
JSONata is a JSON query and transformation language. Prior to 2.2.0 and 1.8.9, malicious non-matching inputs to the $toMillis function can cause superlinear backtracking in the ISO-8601 validation regex, leading to denial of service in applications that evalu…
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High 7.5
HTTP::Date versions before 6.08 for Perl allow CPU exhaustion via polynomial regex backtracking in parse_date
HTTP::Date versions before 6.08 for Perl allow CPU exhaustion via polynomial regex backtracking in parse_date. parse_date() matches the date string against a chain of alternative regexes, and str2time() delegates to it. Several of these patterns place unbound…
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Medium 6.5
Grav < 2.0.4 ReDoS via regex_replace in Sandbox
Grav before 2.0.4 contains a regular expression denial of service (ReDoS) vulnerability in the regex_replace filter and function, which are allowlisted in the Twig content sandbox. When Twig processing in page content is enabled (security.twig_content.process…
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High 7.5
HAPI FHIR: ReDoS via FHIRPath matches()/replaceMatches() in FHIR Validator HTTP Endpoint
HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.7, the FHIRPathEngine implementation passes user-controlled regular expressions from matches(), matchesFull(), and replaceMatches() to Java r…
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Medium 5.3
UAParser.js: Unbounded `Sec-CH-UA-Model` parsing can trigger ReDoS in `withClientHints()`
UAParser.js is a JavaScript library to detect browsers, operating systems, CPUs, and devices from user-agent data. From 2.0.1 until 2.0.10, a regular expression denial-of-service vulnerability exists when using the Client Hints API. By sending a crafted Sec-C…
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High 7.5
Soup Sieve: Regular Expression Denial of Service (ReDoS) in soupsieve Selector Parser
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminat…
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High 8.7
linkify-it: Quadratic algorithmic complexity in LinkifyIt#match scan loop
linkify-it is a links recognition library with full Unicode support. Prior to 5.0.1, LinkifyIt.prototype.match, the package's primary public API, has O(N²) algorithmic complexity for inputs containing many fuzzy links or emails because the JavaScript-level sc…
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High 8.7
Symfony: YAML Parser ReDoS via Catastrophic Backtracking in Parser::cleanup() Regex
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, Symfony\Component\Yaml\Parser::cleanup() used regular expressions with overlapping quantifiers for YAML directive, c…
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High 8.2
Symfony: [Yaml] Harden the parser when handling untrusted input
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-le…
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High 8.2
Symfony: JsonPath Evaluates Attacker-Controlled Regular Expressions in match()/search() Without Limits — ReDoS
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() wit…
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Medium 6.5
Crafted message attachment causes client-side denial of service via markdown parser regex backtracking in Mattermost
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 c…
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High 8.7
Phalcon: Catastrophic backtracking (ReDoS) in the default Phalcon Router route lead to remote unauthenticated DoS
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 …
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Medium 6.5
Open WebUI: ReDoS in skill-mention regexes causes whole-instance DoS on default config
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 overlap…
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High 7.5
HAPI FHIR: DSTU2 FHIRPathEngine.matches() missing RegexTimeout protection allows ReDoS
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/FHIRPathEn…
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Medium 6.5
Guardrails-detectors: guardrails-detectors: unauthenticated regular-expression denial of service (redos) via detector_params.regex
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. …
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High 7.5
Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions
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 h…
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High 7.5
inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs
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 fo…
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High 7.5
Mistune plugins/formatting: quadratic-time parsing on long runs of `~~x~~`, `==x==`, and `^^x^^` markers (strikethrough / mark / insert)
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 plu…
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High 7.5
String::Util versions before 1.36 for Perl are susceptible to a regular expression denial of service
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 chara…
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High 8.7
vLLM: ReDoS via structured_outputs.regex compiled without timeout in xgrammar and outlines backends
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 ti…
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Medium —
@asymmetric-effort/nogginlessdom vulnerable to ReDoS via user-controlled regex in HTMLInputElement pattern validation
## Summary The `HTMLInputElement.checkValidity()` method constructed a `RegExp` directly from the user-controlled `pattern` property without any sanitization or timeout protection. This allowed an attacker to inject a regex with catastrophic backtracking, fre…
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Medium 6.5
LobeChat < 2.2.10-canary.15 - Regular Expression Denial of Service in GitHub Skill Import
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…
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High 7.5
Sentry: Inefficient Regular Expression Complexity in sentry
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 ev…
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High 8.7
Mistune: Potential DoS via quadratic-time parsing in parse_link_text
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,…