CVE-2026-27795

Vulnerability Description

LangChain is a framework for building LLM-powered applications. Prior to version 1.1.8, a redirect-based Server-Side Request Forgery (SSRF) bypass exists in `RecursiveUrlLoader` in `@langchain/community`. The loader validates the initial URL but allows the underlying fetch to follow redirects automatically, which permits a transition from a safe public URL to an internal or metadata endpoint without revalidation. This is a bypass of the SSRF protections introduced in 1.1.14 (CVE-2026-26019). Users should upgrade to `@langchain/community` 1.1.18, which validates every redirect hop by disabling automatic redirects and re-validating `Location` targets before following them. In this version, automatic redirects are disabled (`redirect: "manual"`), each 3xx `Location` is resolved and validated with `validateSafeUrl()` before the next request, and a maximum redirect limit prevents infinite loops.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• https://github.com/langchain-ai/langchainjs/commit/2812d2b2b9fd9343c4850e2ab906bPatch
• https://github.com/langchain-ai/langchainjs/commit/d5e3db0d01ab321ec70a875805b2fPatch
• https://github.com/langchain-ai/langchainjs/pull/9990Issue Tracking
• https://github.com/langchain-ai/langchainjs/releases/tag/%40langchain%2FcommunitRelease Notes
• https://github.com/langchain-ai/langchainjs/releases/tag/%40langchain%2FcommunitRelease Notes
• https://github.com/langchain-ai/langchainjs/security/advisories/GHSA-gf3v-fwqg-4Not Applicable
• https://github.com/langchain-ai/langchainjs/security/advisories/GHSA-mphv-75cg-5Vendor Advisory