Summary
Workarounds
If upgrading is not immediately possible:
- Block
POST /prompts/testat your reverse proxy or API gateway. - Review and rotate API keys that should not have access to prompt management routes.
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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
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.
Frequently Asked Questions
- What is CVE-2026-42203? CVE-2026-42203 is a high-severity security vulnerability in litellm (pip), affecting versions >= 1.80.5, < 1.83.7. It is fixed in 1.83.7.
- Which versions of litellm are affected by CVE-2026-42203? litellm (pip) versions >= 1.80.5, < 1.83.7 is affected.
- Is there a fix for CVE-2026-42203? Yes. CVE-2026-42203 is fixed in 1.83.7. Upgrade to this version or later.
- Is CVE-2026-42203 exploitable, and should I be worried? Whether CVE-2026-42203 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-42203 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-42203? Upgrade
litellmto 1.83.7 or later.