LangChain Community: redirect chaining can lead to SSRF bypass via RecursiveUrlLoader

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:N/A:N

EPSS

• CVE-2026-27795: 0.25% estimated exploitation activity in the next 30 days; percentile 16.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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). Affected Component - Package: @langchain/community - Component: RecursiveUrlLoader - Configuration: preventOutside (default: true) is insufficient to prevent this bypass when redirects are followed automatically. Description RecursiveUrlLoader is a web crawler that recursively follows links from a starting URL. The existing SSRF mitigation validates the initial URL before fetching, but it does not re-validate when the request follows redirects. Because fetch follows redirects by default, an attacker can supply a public URL that passes validation and then redirects to a private…

Published by the source

25 Feb 2026, 22:59 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mphv-75cg-56wg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-mphv-75cg-56wg

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# Patch Next advisory brief: CVE-2026-27795

Advisory: LangChain Community: redirect chaining can lead to SSRF bypass via RecursiveUrlLoader
IDs: CVE-2026-27795, GHSA-mphv-75cg-56wg
Record: https://patchnext.com/advisories/cve-2026-27795 (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @langchain/community 1.1.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @langchain/community: affected <= 1.1.17; fixed in 1.1.18

## Suggested inspection (read-only)
- `npm ls @langchain/community --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @langchain/community.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-mphv-75cg-56wg (OSV record GHSA-mphv-75cg-56wg lists affected ranges: npm @langchain/community >=0 <1.1.18 (fixed))
- Verified: https://github.com/advisories/GHSA-mphv-75cg-56wg (GitHub-reviewed advisory GHSA-mphv-75cg-56wg lists affected ranges: npm @langchain/community >=0 <=1.1.17)

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