- CVSS
- MEDIUM · 4.1 v3.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:N/A:N
- Published
- 2026-02-25
- Weakness
- CWE-918
- Source
- nvd.nist.gov/vuln/detail/CVE-2026-27795
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.
References
- https://github.com/langchain-ai/langchainjs/commit/2812d2b2b9fd9343c4850e2ab906b8cf440975ee
- https://github.com/langchain-ai/langchainjs/commit/d5e3db0d01ab321ec70a875805b2f74aefdadf9d
- https://github.com/langchain-ai/langchainjs/pull/9990
- https://github.com/langchain-ai/langchainjs/releases/tag/%40langchain%2Fcommunity%401.1.14
- https://github.com/langchain-ai/langchainjs/releases/tag/%40langchain%2Fcommunity%401.1.18
- https://github.com/langchain-ai/langchainjs/security/advisories/GHSA-gf3v-fwqg-4vh7
How GTK Cyber trains on this
AI security training at GTK Cyber covers the LLM and ML-pipeline vulnerability classes that vulnerabilities like CVE-2026-27795 fall into. Our hands-on courses are taught by Charles Givre and other practitioners who break and defend production AI systems.