How severe is CVE-2026-42203?

No CVSS score has been assigned to CVE-2026-42203 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42203?

CVE-2026-42203 affects the following packages: litellm (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-42203?

Update litellm to 1.83.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42203 is resolved across your whole dependency graph.

How do I detect CVE-2026-42203 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for litellm, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42203 if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is CVE-2026-42203 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42203 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42203?

CVE-2026-42203 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42203?

CVE-2026-42203 is classified as CWE-1336 (CWE-1336), Code Injection (CWE-94). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-42203 published, and has it been updated?

CVE-2026-42203 was published on May 8, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-42203 — litellm

CVE-2026-42203 is a CWE-1336 vulnerability in litellm. A fix is available for litellm — see the affected versions and patch details below.

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

Also known asGHSA-xqmj-j6mv-4862PYSEC-2026-2602

Published

May 8, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42203.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍litellm

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`litellm`	≥ 1.80.5&&< 1.83.7	1.83.7`pip install --upgrade 'litellm==1.83.7'`

Affected Products

1 product · 1 configurations

Application

litellmlitellm

≥ 1.80.5 && < 1.83.7

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for litellm, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update litellm to 1.83.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42203 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Important: This flaw in LiteLLM, an AI Gateway, allows an authenticated user to achieve arbitrary code execution by sending a crafted prompt template to the /prompts/test endpoint. This is considered Important due to the potential for exposure of sensitive information, such as API keys or database credentials, and the…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for CVE-2026-42203 (CC BY 4.0)

Frequently Asked Questions

### 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

O3 Security · Impact-Aware SCA

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