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

> Attackers can inject malicious URLs via HTTP headers in the LangSmith SDK, causing sensitive trace data to be sent to attacker-controlled endpoints.

- **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Feb 2026
- **Updated:** 10 Feb 2026
- **Also known as:** ECHO-f9e2-5c88-6463, GHSA-v34v-rq6j-cj6p, MINI-6xxj-g8px-5m8q, MINI-757g-82c7-r5h3, MINI-jpc4-q8gv-fw23, MINI-qm5h-jf8w-288v, PYSEC-2026-2584, ROOT-APP-PYPI-CVE-2026-25528

## What is CVE-2026-25528?

CVE-2026-25528 is a medium-severity server-side request forgery vulnerability in langchain-ai langsmith-sdk, published on 9 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-25528?

5 open source packages ship an affected version, including langsmith.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `langsmith` | PyPI | From 0.4.10 | 0.6.3 |
| `langsmith` | PyPI | From 0.4.10 | 0.6.3 |
| `langsmith` | PyPI | From 0.4.10 | 0.6.3 |
| `langsmith` | npm | From 0.3.41 | 0.4.6 |
| `langsmith` | npm | From 0.3.41 | 0.4.6 |

## How do I fix CVE-2026-25528?

Upgrade langsmith to a fixed version for your release line: 0.6.3 or 0.4.6.

## Is CVE-2026-25528 being exploited?

There is no known exploitation of CVE-2026-25528 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-25528 and fix it if it is affected.

What it is: CVE-2026-25528 is a medium-severity server-side request forgery vulnerability in langchain-ai langsmith-sdk, published on 9 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-25528 in the wild and no public exploit code.

Affected packages and fixed versions:
- langsmith (PyPI): affected from 0.4.10; fixed in 0.6.3
- langsmith (PyPI): affected from 0.4.10; fixed in 0.6.3
- langsmith (PyPI): affected from 0.4.10; fixed in 0.6.3
- langsmith (npm): affected from 0.3.41; fixed in 0.4.6
- langsmith (npm): affected from 0.3.41; fixed in 0.4.6

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-25528/ (Markdown: https://insights.sbomify.com/CVE-2026-25528/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-25528
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-25528
- OSV: https://osv.dev/vulnerability/CVE-2026-25528

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-25528/
Summaries are generated and may contain mistakes; the official description above is the record.