CVE-2026-27795

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.

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

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.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-27795 has a CVSS score of 4.1 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.1.18); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-27795? CVE-2026-27795 is a medium-severity server-side request forgery (SSRF) vulnerability in @langchain/community (npm), affecting versions <= 1.1.17. It is fixed in 1.1.18. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-27795? CVE-2026-27795 has a CVSS score of 4.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @langchain/community are affected by CVE-2026-27795? @langchain/community (npm) versions <= 1.1.17 is affected.
4. Is there a fix for CVE-2026-27795? Yes. CVE-2026-27795 is fixed in 1.1.18. Upgrade to this version or later.
5. Is CVE-2026-27795 exploitable, and should I be worried? Whether CVE-2026-27795 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-27795 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-27795? Upgrade @langchain/community to 1.1.18 or later.