CVE WatchJul 14, 2026

CVE-2024-58340

LangChain versions up to and including 0.3.1 contain a regular expression denial-of-service (ReDoS) vulnerability in the MRKLOutputParser.pa

CVSS

7.5

High

EPSS

0.4%

p33

KEV

—

Exploit Today

0-100

Published: Jan 12, 2026 · Last modified: Jul 14, 2026 · CWE-1333

EPSS · 30d

0.4%EPSS · 30 days0.4%

2026-06-302026-07-20

Technical description

LangChain versions up to and including 0.3.1 contain a regular expression denial-of-service (ReDoS) vulnerability in the MRKLOutputParser.parse() method (libs/langchain/langchain/agents/mrkl/output_parser.py). The parser applies a backtracking-prone regular expression when extracting tool actions from model output. An attacker who can supply or influence the parsed text (for example via prompt injection in downstream applications that pass LLM output directly into MRKLOutputParser.parse()) can trigger excessive CPU consumption by providing a crafted payload, causing significant parsing delays and a denial-of-service condition.

Official references

Related CVEs

CVECVSSEPSSKEVRExploitTitleMod.

CVE-2022-421247.5 HIG

65.7%

——20ReDoS vulnerability in LayoutPageTemplateEntryUpgradeProcess in Liferay Portal 7.3.2 through 7.4.3.4 and Liferay DXP 7.2 fix pack 9 through fix pack 18, 7.3 before update 4, and DXP 7.4 GA allows remote attackers to consume an excessive amount of server resources via a crafted payload injected into the 'name' field of a layout prototype.12d CVE-2026-49267.5 HIG

52.3%

——16Impact: 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.4d CVE-2026-453057.5 HIG

50.9%

——15Symfony 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, comment, and document marker cleanup, allowing crafted input to make parsing hang for an arbitrarily long time. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.6d CVE-2024-462427.5 HIG

49.3%

——15An 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.16d CVE-2026-283567.5 HIG

49.1%

——15multipart 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.6d CVE-2026-451337.5 HIG

48.8%

——15Symfony 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 8.0.12.6d