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CWE-1333

Inefficient Regular Expression Complexity

BaseDraftLikelihood: High

Description

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

Hierarchy (View 1000)

Parents

Children

none

Related attack patterns (CAPEC)

CAPEC-492

CVEs mapped to this weakness (78)

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CVESevRiskCVSSEPSSKEVPublishedDescription
CVE-2026-25547Cri0.60—0.00Feb 4, 2026@isaacs/brace-expansion is a hybrid CJS/ESM TypeScript fork of brace-expansion. Prior to version 5.0.1, @isaacs/brace-expansion is vulnerable to a denial of service (DoS) issue caused by unbounded brace range expansion. When an attacker provides a pattern containing repeated numeric brace ranges, the library attempts to eagerly generate every possible combination synchronously. Because the expansion grows exponentially, even a small input can consume excessive CPU and memory and may crash the Node.js process. This issue has been patched in version 5.0.1.
CVE-2026-35458Cri0.579.80.00Apr 7, 2026Gotenberg is an API for converting document formats. In 8.29.1 and earlier, Gotenberg uses dlclark/regexp2 to compile user-supplied scope patterns without setting a proper timeout. Users with access to features using this logic can hang workers indefinitely.
CVE-2025-6998Hig0.57—0.00Jul 24, 2025ReDoS in strip_whitespaces() function in cps/string_helper.py in Calibre Web and Autocaliweb allows unauthenticated remote attackers to cause denial of service via specially crafted username parameter that triggers catastrophic backtracking during login. This issue affects Calibre Web: 0.6.24 (Nicolette); Autocaliweb: from 0.7.0 before 0.7.1.
CVE-2020-26310Hig0.57—0.00Oct 26, 2024Validate.js provides a declarative way of validating javascript objects. All versions as of 30 November 2020 contain one or more regular expressions that are vulnerable to Regular Expression Denial of Service (ReDoS). As of time of publication, it is unknown if any patches are available.
CVE-2020-26307Hig0.57—0.00Oct 26, 2024HTML2Markdown is a Javascript implementation for converting HTML to Markdown text. All available versions contain one or more regular expressions that are vulnerable to Regular Expression Denial of Service (ReDoS). As of time of publication, no known patches are available.
CVE-2025-58451Hig0.50—0.00Sep 8, 2025Cattown is a JavaScript markdown parser. Versions prior to 1.0.2 used regular expressions with inefficient, potentially exponential worst-case complexity. This could cause excessive CPU usage due to excessive backtracking on crafted inputs. In turn, the excessive CPU usage could lead to resource exhaustion, where processing malicious inputs could cause high CPU or memory usage, potentially leading to denial of service. Version 1.0.2 contains a patch. Additionally, users should review and restrict input sources if untrusted inputs are processed.
CVE-2020-26309Hig0.50—0.00Oct 26, 2024Validate.js provides a declarative way of validating javascript objects. Versions 0.11.3 and prior contain one or more regular expressions that are vulnerable to Regular Expression Denial of Service (ReDoS). As of time of publication, it is unknown if any patches are available.
CVE-2020-26306Hig0.50—0.00Oct 26, 2024Knwl.js is a Javascript library that parses through text for dates, times, phone numbers, emails, places, and more. Versions 1.0.2 and prior contain one or more regular expressions that are vulnerable to Regular Expression Denial of Service (ReDoS). As of time of publication, no known patches are available.
CVE-2026-41040Hig0.497.50.00Apr 23, 2026GROWI provided by GROWI, Inc. is vulnerable to a regular expression denial of service (ReDoS) via a crafted input string.
CVE-2026-35611Hig0.497.50.00Apr 7, 2026Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.3.0 to before 2.9.0, within the URI template implementation in Addressable, two classes of URI template generate regular expressions vulnerable to catastrophic backtracking. Templates using the * (explode) modifier with any expansion operator (e.g., {foo*}, {+var*}, {#var*}, {/var*}, {.var*}, {;var*}, {?var*}, {&var*}) generate patterns with nested unbounded quantifiers that are O(2^n) when matched against a maliciously crafted URI. Templates using multiple variables with the + or # operators (e.g., {+v1,v2,v3}) generate patterns with O(n^k) complexity due to the comma separator being within the matched character class, causing ambiguous backtracking across k variables. When matched against a maliciously crafted URI, this can result in catastrophic backtracking and uncontrolled resource consumption, leading to denial of service. This vulnerability is fixed in 2.9.0.
CVE-2026-35213Hig0.497.50.00Apr 6, 2026@hapi/content provided HTTP Content-* headers parsing. All versions of @hapi/content through 6.0.0 are vulnerable to Regular Expression Denial of Service (ReDoS) via crafted HTTP header values. Three regular expressions used to parse Content-Type and Content-Disposition headers contain patterns susceptible to catastrophic backtracking. This vulnerability is fixed in 6.0.1.
CVE-2026-4926Hig0.497.50.00Mar 26, 2026Impact: A bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service. Patches: Fixed in version 8.4.0. Workarounds: Limit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.
CVE-2026-4867Hig0.497.50.00Mar 26, 2026Impact: A bad regular expression is generated any time you have three or more parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b-:c or /:a-:b-:c-:d. The backtrack protection added in path-to-regexp@0.1.12 only prevents ambiguity for two parameters. With three or more, the generated lookahead does not block single separator characters, so capture groups overlap and cause catastrophic backtracking. Patches: Upgrade to path-to-regexp@0.1.13 Custom regex patterns in route definitions (e.g., /:a-:b([^-/]+)-:c([^-/]+)) are not affected because they override the default capture group. Workarounds: All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b-:c to /:a-:b([^-/]+)-:c([^-/]+). If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length.
CVE-2026-28356Hig0.497.50.01Mar 12, 2026multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.
CVE-2025-70030Hig0.497.50.00Mar 9, 2026An issue pertaining to CWE-1333: Inefficient Regular Expression Complexity (4.19) was discovered in Sunbird-Ed SunbirdEd-portal v1.13.4.
CVE-2025-70034Hig0.497.50.00Mar 9, 2026An issue pertaining to CWE-1333: Inefficient Regular Expression Complexity (4.19) was discovered in mscdex ssh2 v1.17.0.
CVE-2025-10990Hig0.497.50.00Feb 27, 2026A flaw was found in REXML. A remote attacker could exploit inefficient regular expression (regex) parsing when processing hex numeric character references (&#x...;) in XML documents. This could lead to a Regular Expression Denial of Service (ReDoS), impacting the availability of the affected component. This issue is the result of an incomplete fix for CVE-2024-49761.
CVE-2024-7779Hig0.497.50.00Mar 20, 2025A vulnerability in danswer-ai/danswer version 1 allows an attacker to perform a Regular Expression Denial of Service (ReDoS) by manipulating regular expressions. This can significantly slow down the application's response time and potentially render it completely unusable.
CVE-2024-46242Hig0.497.50.00Jan 7, 2025An issue in the validate_email function in CTFd/utils/validators/__init__.py of CTFd 3.7.3 allows attackers to cause a Regular expression Denial of Service (ReDoS) via supplying a crafted string as e-mail address during registration.
CVE-2024-25885Hig0.497.50.00Oct 8, 2024An issue in the getcolor function in utils.py of xhtml2pdf v0.2.13 allows attackers to cause a Regular expression Denial of Service (ReDOS) via supplying a crafted string.