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GHSA-mphv-75cg-56wg

MediumCVSS 4.1 / 10
Published Feb 25, 2026·Last modified Feb 25, 2026
Affected Components(0)

No affected components available

Description

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 network address, localhost, or cloud metadata endpoint.

This constitutes a “check‑then‑act” gap in the request lifecycle: the safety check occurs before the redirect chain is resolved, and the final destination is never validated.

Impact

If an attacker can influence content on a page being crawled (e.g., user‑generated content, untrusted external pages), they can cause the crawler to:

  • Fetch cloud instance metadata (AWS, GCP, Azure), potentially exposing credentials or tokens
  • Access internal services on private networks (10.x, 172.16.x, 192.168.x)
  • Connect to localhost services
  • Exfiltrate response data through attacker-controlled redirect chains

This is exploitable in any environment where RecursiveUrlLoader runs with access to internal networks or metadata services, which includes most cloud-hosted deployments.

Attack Scenario

  1. The crawler is pointed at a public URL that passes initial SSRF validation.
  2. That URL responds with a 3xx redirect to an internal target.
  3. The fetch follows the redirect automatically without revalidation.
  4. The crawler accesses the internal or metadata endpoint.

Example redirector:

https://302.r3dir.me/--to/?url=http://169.254.169.254/latest/meta-data/

Root Cause

  • SSRF validation (validateSafeUrl) is only performed on the initial URL.
  • Redirects are followed automatically by fetch (redirect: "follow" default), so the request can change destinations without additional validation.

Resolution

Upgrade to @langchain/community >= 1.1.18, which validates every redirect hop by disabling automatic redirects and re-validating Location targets before following them.

  • Automatic redirects are disabled (redirect: "manual").
  • Each 3xx Location is resolved and validated with validateSafeUrl() before the next request.
  • A maximum redirect limit prevents infinite loops.

Reources

  • Original SSRF fix (CVE-2026-26019): enforced origin comparison and added initial URL validation
  • https://github.com/langchain-ai/langchainjs/security/advisories/GHSA-gf3v-fwqg-4vh7
Risk Scores
Base Score
4.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information.

Threat Intelligence
3.8

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.21%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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