CVE-2026-26019

Description

The RecursiveUrlLoader class in @langchain/community is a web crawler that recursively follows links from a starting URL. Its preventOutside option (enabled by default) is intended to restrict crawling to the same site as the base URL.

The implementation used String.startsWith() to compare URLs, which does not perform semantic URL validation. An attacker who controls content on a crawled page could include links to domains that share a string prefix with the target (e.g., https://example.com.attacker.com passes a startsWith check against https://example.com), causing the crawler to follow links to attacker-controlled or internal infrastructure.

Additionally, the crawler performed no validation against private or reserved IP addresses. A crawled page could include links targeting cloud metadata services (169.254.169.254), localhost, or RFC 1918 addresses, and the crawler would fetch them without restriction.

Resolution

Two changes were made:

1. Origin comparison replaced. The startsWith check was replaced with a strict origin comparison using the URL API (new URL(link).origin === new URL(baseUrl).origin). This correctly validates scheme, hostname, and port as a unit, preventing subdomain-based bypasses.

2. SSRF validation added to all fetch operations. A new URL validation module (@langchain/core/utils/ssrf) was introduced and applied before every outbound fetch in the crawler. This blocks requests to:

   • Cloud metadata endpoints: 169.254.169.254, 169.254.170.2, 100.100.100.200, metadata.google.internal, and related hostnames
   • Private IP ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 127.0.0.0/8, 169.254.0.0/16
   • IPv6 equivalents: ::1, fc00::/7, fe80::/10
   • Non-HTTP/HTTPS schemes (file:, ftp:, javascript:, etc.)

Cloud metadata endpoints are unconditionally blocked and cannot be overridden.

Workarounds

Users who cannot upgrade immediately should avoid using RecursiveUrlLoader on untrusted or user-influenced content, or should run the crawler in a network environment without access to cloud metadata or internal services.

An attacker who can influence the content of a page being crawled (e.g., by placing a link on a public-facing page, forum, or user-generated content) could cause the crawler to:

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

This is exploitable in any environment where RecursiveUrlLoader runs on infrastructure with access to cloud metadata or internal 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-2026-26019 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 (1.1.14); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-26019? CVE-2026-26019 is a medium-severity server-side request forgery (SSRF) vulnerability in @langchain/community (npm), affecting versions <= 1.1.13. It is fixed in 1.1.14. 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-2026-26019? CVE-2026-26019 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-2026-26019? @langchain/community (npm) versions <= 1.1.13 is affected.
4. Is there a fix for CVE-2026-26019? Yes. CVE-2026-26019 is fixed in 1.1.14. Upgrade to this version or later.
5. Is CVE-2026-26019 exploitable, and should I be worried? Whether CVE-2026-26019 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-2026-26019 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-2026-26019? Upgrade @langchain/community to 1.1.14 or later.