How severe is CVE-2026-42271?

No CVSS score has been assigned to CVE-2026-42271 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42271?

CVE-2026-42271 affects the following packages: litellm (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-42271?

Update litellm to 1.83.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42271 is resolved across your whole dependency graph.

How do I detect CVE-2026-42271 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-2026-42271 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-2026-42271 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42271 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-2026-42271?

CVE-2026-42271 has an EPSS (Exploit Prediction Scoring System) score of 92.6%, placing it in the 100th 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2026-42271?

CVE-2026-42271 is classified as CWE-77 (CWE-77), OS Command Injection (CWE-78). 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.

Is there exploit tooling available for CVE-2026-42271?

A Nuclei detection template exists for CVE-2026-42271, meaning automated scanners can fingerprint it. 2 Metasploit modules reference CVE-2026-42271, which lowers the barrier to weaponization. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2026-42271 published, and has it been updated?

CVE-2026-42271 was published on May 8, 2026 and was last updated on October 21, 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-2026-42271 — litellm

CVE-2026-42271 is a CWE-77 vulnerability in litellm. EPSS puts its 30-day exploitation probability at 92.6% (100th percentile). A fix is available for litellm — see the affected versions and patch details below.

LiteLLM: Authenticated command execution via MCP stdio test endpoints

Also known asGHSA-v4p8-mg3p-g94gPYSEC-2026-2599

Published

May 8, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

CISA’s SSVC triage classifies this CVE as under active exploitation.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42271.

EPSS Exploitation Probability

via FIRST.org ↗

92.6%probability of exploitation in next 30 days

Very High Risk0.00%

Lower risk than most CVEs100th percentile — riskier than 100% 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

Two endpoints used to preview an MCP server before saving it — POST /mcp-rest/test/connection and POST /mcp-rest/test/tools/list — accepted a full server configuration in the request body, including the command, args, and env fields used by the stdio transport. When called with a stdio configuration, the endpoints attempted to connect, which spawned the supplied command as a subprocess on the proxy host with the privileges of the proxy process.

The endpoints were gated only by a valid proxy API key, with no role check. Any authenticated user — including holders of low-privilege internal-user keys — could therefore run arbitrary commands on the host.

Patches

Fixed in 1.83.7. Both test endpoints now require the PROXY_ADMIN role, bringing them into line with the save endpoint.

Workarounds

If upgrading is not immediately possible, developers should block POST /mcp-rest/test/connection and POST /mcp-rest/test/tools/list at their reverse proxy or API gateway.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`litellm`	≥ 1.74.2&&< 1.83.7	1.83.7`pip install --upgrade 'litellm==1.83.7'`

Affected Products

2 products · 4 configurations

Application

litellmlitellm

≥ 1.74.2 && < 1.83.7

range

Application

openshift airedhat

≥ 3.3 && < 3.3.4

1 version

3.4

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-2026-42271 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.

How to detect CVE-2026-42271

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2026-42271 -u https://target

Template: LiteLLM - Command Injection
Severity: critical
Impact: Successful exploitation allows unauthenticated remote attackers to execute arbitrary commands on affected LiteLLM instances, potentially leading to full system compromise, lateral movement, data theft, and persistent access.
Remediation: Upgrade LiteLLM to version 1.83.7 or later to remediate this vulnerability. If immediate patching is not possible, restrict access to the `/mcp-rest/test/connection` endpoint and ensure authentication verification is robust.

Template by ProjectDiscovery nuclei-templates (ritikchaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.

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

This is an Important flaw affecting LiteLLM, as deployed in Red Hat products like Ansible Automation Platform and OpenShift AI. Authenticated users, even with low-privilege API keys, can execute arbitrary commands on the proxy host. This is due to insufficient role checks on specific endpoints that accept server…

Product	Fixed in	Advisory
Red Hat OpenShift AI 2.25	`rhoai/odh-llama-stack-core-rhel9:1781826406`	RHSA-2026:28960
Red Hat OpenShift AI 3.3	`rhoai/odh-llama-stack-core-rhel9:1782310008`	RHSA-2026:30056
Red Hat OpenShift AI 3.4	`rhoai/odh-trustyai-garak-lls-provider-dsp-rhel9:1781622627`	RHSA-2026:27784

Frequently Asked Questions

### Impact Two endpoints used to preview an MCP server before saving it — `POST /mcp-rest/test/connection` and `POST /mcp-rest/test/tools/list` — accepted a full server configuration in the request body, including the `command`, `args`, and `env` fields used by the stdio transport. When called with a stdio configuration, the endpoints attempted to connect, which spawned the supplied command as a subprocess on the proxy host with the privileges of the proxy process. The endpoints were gated only by a valid proxy API key, with no role check. Any authenticated user — including holders of low-pr

O3 Security · Impact-Aware SCA

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