CVE-2024-58340
Unknown Unknown - Not Provided
ReDoS Vulnerability in LangChain MRKLOutputParser Causes DoS

Publication date: 2026-01-12

Last updated on: 2026-01-12

Assigner: VulnCheck

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.
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Meta Information
Published
2026-01-12
Last Modified
2026-01-12
Generated
2026-05-07
AI Q&A
2026-01-13
EPSS Evaluated
2026-05-05
NVD
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
langchain langchain to 0.3.1 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-1333 The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a Regular Expression Denial of Service (ReDoS) in LangChain versions up to 0.3.1, specifically in the MRKLOutputParser.parse() method. The parser uses a backtracking-prone regular expression to extract tool actions from model output. An attacker who can supply or influence the parsed text, for example via prompt injection in applications that pass LLM output directly into this parser, can craft input that causes excessive CPU consumption. This leads to significant parsing delays and can cause a denial-of-service condition. [3]


How can this vulnerability impact me? :

If exploited, this vulnerability can cause excessive CPU usage on systems running vulnerable LangChain versions, leading to significant delays in parsing operations and potentially causing denial-of-service conditions. This means that applications relying on the MRKLOutputParser.parse() method may become unresponsive or slow, disrupting service availability. [3]


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