CVE-2026-25528: PYSEC-2026-2584 - LangSmith Client SDK Affected by Server-Side Request Forgery via Tracing Header Injection

CVE-2026-25528 · Severity: low · CVSS 3.1 · Published 2026-07-13

LangSmith SDK is a library used by developers to trace and monitor Large Language Model (LLM) application behavior. The SDK's distributed tracing feature accepts untrusted HTTP headers that can be manipulated to inject malicious URLs. An attacker can force the SDK to send sensitive application data—including LLM prompts, outputs, and metadata—to attacker-controlled servers, enabling data theft and internal network probing.

Technologies: LangChain LangSmith SDK, langsmith (npm), langsmith (PyPI). Vendors: LangChain, npm, PyPI.

Quick answers

Is CVE-2026-25528 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-25528 being exploited in the wild.
How severe is CVE-2026-25528?
Low severity, with a CVSS score of 3.1, published 13 July 2026.
Which products and versions are affected?
LangChain LangSmith SDK Python >=0.4.10, <0.6.3; TypeScript >=0.3.41, <0.4.6; langsmith (npm) SEMVER:introduced=0.3.41,fixed=0.4.6; langsmith (PyPI) ECOSYSTEM:introduced=0.4.10,fixed=0.6.3.
Is there a fix for CVE-2026-25528?
Yes. langsmith (npm): upgrade to 0.4.6 or later; langsmith (PyPI): upgrade to 0.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-25528 attacked?
It is attacked over the network.
Am I affected by CVE-2026-25528?
Check whether you run LangChain LangSmith SDK, langsmith (npm) or langsmith (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • langsmith (npm): upgrade to 0.4.6 or later
    npm install langsmith@0.4.6
  • langsmith (PyPI): upgrade to 0.6.3 or later
    pip install "langsmith>=0.6.3"

Technical details

The vulnerability is a Server-Side Request Forgery (CWE-918) in the SDK's distributed tracing feature, specifically in the RunTree.from_headers() (Python) and RunTree.fromHeaders() (TypeScript) functions. These functions parse the baggage HTTP header without validating the api_url and api_key fields, allowing an attacker to inject arbitrary replica URLs. When a traced operation completes, the SDK sends run data (including LLM inputs, outputs, and metadata) to all configured replicas, including attacker-injected endpoints. The attack requires no privileges or user interaction—any application using TracingMiddleware or calling from_headers() with untrusted HTTP headers is vulnerable. Patches are available: Python ≥0.6.3 and TypeScript ≥0.4.6 remove credential fields from parsed replica configurations via an allowlist mechanism.

Affected products

  • LangChain LangSmith SDK Python >=0.4.10, <0.6.3; TypeScript >=0.3.41, <0.4.6

Identifiers

  • CVE-2026-25528
  • GHSA-v34v-rq6j-cj6p
  • PYSEC-2026-2584

Timeline

  • 2026-02-09: disclosed: GHSA-v34v-rq6j-cj6p and CVE-2026-25528 published
  • 2026-02-09: patched: Python 0.6.3 and TypeScript 0.4.6 released with fix

References

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