CVE-2026-25528: langchain-ai langsmith-sdk Server-Side Request Forgery (SSRF)

Vulnerability summary

CVE-2026-25528 is a medium (CVSS 5.8) Server-Side Request Forgery (SSRF) vulnerability in langchain-ai langsmith-sdk. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 28.7% of scored vulnerabilities.

Timeline

1. 09-02-2026
   PublishedVulnerability first disclosed.
2. 10-02-2026
   Last modifiedVulnerability information updated.

Description

LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. The LangSmith SDK's distributed tracing feature is vulnerable to Server-Side Request Forgery via malicious HTTP headers. An attacker can inject arbitrary api_url values through the baggage header, causing the SDK to exfiltrate sensitive trace data to attacker-controlled endpoints. When using distributed tracing, the SDK parses incoming HTTP headers via RunTree.from_headers() in Python or RunTree.fromHeaders() in Typescript. The baggage header can contain replica configurations including api_url and api_key fields. Prior to the fix, these attacker-controlled values were accepted without validation. When a traced operation completes, the SDK's post() and patch() methods send run data to all configured replica URLs, including any injected by an attacker. This vulnerability is fixed in version 0.6.3 of the Python SDK and 0.4.6 of the JavaScript SDK.

• CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.