CVE-2024-58340

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.

• CWE-1333

• https://github.com/langchain-ai/langchainProduct
• https://huntr.com/bounties/e7ece02c-d4bb-4166-8e08-6baf4f8845bbExploit, Issue Tracking, Third Party Advisory
• https://www.langchain.com/Product
• https://www.vulncheck.com/advisories/langchain-mrkloutputparser-redosThird Party Advisory

Published

Jan 12, 2026

Last Modified

Jul 14, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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