AI agent vulnerability · LiteLLM

CVE-2026-42203: LiteLLM: Server-Side Template Injection in /prompts/test endpoint

highCVSS 4.0 8.6GHSA-xqmj-j6mv-4862

Impact The POST /prompts/test endpoint accepted user-supplied prompt templates and rendered them without sandboxing. A crafted template could run arbitrary code inside the LiteLLM Proxy process. The endpoint only checks that the caller presents a valid proxy API key, so any authenticated user could reach it.

Published Apr 24, 2026 · Updated May 12, 2026

Affected packages

litellm

Ecosystem: PyPI
Affected: >= 1.80.5, < 1.83.7
Fixed in: 1.83.7
Check: pip show litellm

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

Impact

The POST /prompts/test endpoint accepted user-supplied prompt templates and rendered them without sandboxing. A crafted template could run arbitrary code inside the LiteLLM Proxy process.

The endpoint only checks that the caller presents a valid proxy API key, so any authenticated user could reach it. Depending on how the proxy is deployed, this could expose secrets in the process environment (such as provider API keys or database credentials) and allow commands to be run on the host.

Proxy deployments running an affected version are in scope.

Patches

The issue is fixed in `1.83.7-stable`. The fix switches the prompt template renderer to a sandboxed environment that blocks the attributes this attack relies on.

LiteLLM recommends upgrading to 1.83.7-stable or later.

Workarounds

If upgrading is not immediately possible:

Block POST /prompts/test at your reverse proxy or API gateway.
Review and rotate API keys that should not have access to prompt management routes.

References

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

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