CVE-2026-59152 Arbitrary server-side file read in LangSmith SDK TracingMiddleware
An attacker can force a server using LangSmith SDK TracingMiddleware to read arbitrary local files and exfiltrate them to a LangSmith workspace.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-59152?
CVE-2026-59152 is a medium-severity path traversal vulnerability in langchain-ai langsmith-sdk, published on 6 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. Prior to 0.8.18, an attacker who can send an HTTP request to a server running the LangSmith SDK's TracingMiddleware can cause that server to read an arbitrary file from its local filesystem and upload the contents to LangSmith as a trace attachment. Depending on how the distributed trace system is deployed, triggering a read may not require authentication. Retrieving the contents requires read access to the LangSmith workspace the traces are sent to. The net effect is a trust-boundary crossing: a party with workspace trace-read access (for example a low-privilege workspace member, a contractor, or a compromised teammate account) gains the ability to read files from any server running TracingMiddleware, a capability outside that workspace's intended trust boundary. This vulnerability is fixed in 0.8.18.
Which versions are affected by CVE-2026-59152?
2 open source packages ship an affected version, including langsmith.
| Package | Affected | Fixed in |
|---|---|---|
langsmith PyPI | All versions | 0.8.18 |
langsmith PyPI | All versions | 0.8.18 |
How do I fix CVE-2026-59152?
Upgrade langsmith to 0.8.18 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-59152 being exploited?
There is no known exploitation of CVE-2026-59152 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-DI87779, CLEANSTART-2026-EU68751, CLEANSTART-2026-TL07655, ECHO-981d-76df-3620, GHSA-f4xh-w4cj-qxq8, ROOT-APP-PYPI-GHSA-f4xh-w4cj-qxq8.