The Langchain development team has released a critical security update for the @langchain/community package to address a Server-Side Request Forgery (SSRF) vulnerability.
Identified as CVE-2026-26019, this flaw exists within the RecursiveUrlLoader class, a utility used for web crawling.
If left unpatched, the vulnerability allows attackers to bypass domain restrictions and force the application to access internal network resources or sensitive cloud metadata.
SSRF Bypass Vulnerability
The core of the issue lies in how the RecursiveUrlLoader validated URLs during crawling operations.
The utility includes a preventOutside option, enabled by default, which is designed to restrict the crawler to the same website as the starting URL.
However, the implementation relied on a simple string comparison using String.startsWith() rather than a strict semantic validation of the URL origin.
This method creates a significant loophole where an attacker can construct a malicious domain that shares a prefix with the target domain.
For example, if the crawler is set to https://example.com, an attacker could direct it to https://example.com.attacker.com, successfully bypassing the check because the string technically matches the prefix.
Beyond the string matching flaw, the previous version of the crawler lacked validation against private or reserved IP addresses.
This meant that if an attacker could influence the content of a page being crawled, they could inject links pointing to sensitive internal destinations.
The crawler would blindly fetch these resources, including cloud metadata services used by AWS, Google Cloud, and Azure.
Accessing these metadata endpoints is a common technique used by threat actors to steal IAM credentials and session tokens, which can lead to a full compromise of cloud infrastructure.
The crawler could also be directed to scan internal networks or access services running on localhost.
| CVE ID | CVSS Score | Description |
|---|---|---|
| CVE-2026-26019 | 6.1 (Moderate) | An SSRF bypass vulnerability in @langchain/community allows attackers to access internal services and cloud metadata via insufficient URL origin validation in the RecursiveUrlLoader class. |
Affected Packages
| Package | Affected Versions | Patched Version |
|---|---|---|
| @langchain/community | <= 1.1.13 | 1.1.14 |
The Langchain have addressed this vulnerability in version 1.1.14 by implementing two key security improvements.
First, the faulty string comparison has been replaced with a strict origin check using the URL API, ensuring that the scheme, hostname, and port must match exactly.
Second, a new SSRF validation module has been introduced that runs before every outbound request.
This module explicitly blocks connections to private IP ranges, local loopback addresses, and known cloud metadata endpoints such as 169.254.169.254.
Developers using @langchain/community should upgrade to version 1.1.14 immediately.
If an immediate upgrade is not feasible, users are advised to avoid running the RecursiveUrlLoader on untrusted user-generated content or to deploy the application in an isolated network environment with restricted access to internal services and cloud metadata APIs.
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