Threat Intelligence / CVE / CVE-2026-42271

CVE-2026-42271 — Litellm

CISA KEV

CVSS v3.1 8.8 (HIGH) · CVSS v4.0 8.7 · EPSS 92.5% (higher than 99.8% of all scored CVEs) · Priority 9/10 · Published 2026-05-08

As of 2026-07-15, CVE-2026-42271 is a HIGH-severity vulnerability in Litellm, CVSS v3.1 8.8, EPSS 92.5% (99.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-06-08), with a US federal remediation deadline of 2026-06-22. Threadlinqs Intelligence links 4 tracked threat campaigns to CVE-2026-42271, most recently “GTIG: AI-Era Vulnerability Discovery and Exploitation Surge — In-the-Wild Exploitation of BeyondTrust CVE-2026-1731, LiteLLM CVE-2026-42271 and Langflow CVE-2026-5027”.

Last updated: 2026-07-15

What is CVE-2026-42271?

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. From version 1.74.2 to before version 1.83.7, 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. This issue has been patched in version 1.83.7.

The record classifies CVE-2026-42271 under weakness classes CWE-77, CWE-78. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 146 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 8.8 — HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0 base score: 8.7
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:N/SA:N
EPSS (FIRST): 92.5% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
CISA KEV: Listed since 2026-06-08, federal remediation deadline 2026-06-22
Threadlinqs priority: 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published: 2026-05-08, last modified 2026-07-15

Is CVE-2026-42271 being exploited?

CISA added CVE-2026-42271 to the Known Exploited Vulnerabilities catalog on 2026-06-08, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-06-22 under BOD 22-01. Weaponised exploit code for CVE-2026-42271 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2026/CVE-2026-42271.yaml). It currently carries a trending score of 45 in the Threadlinqs vulnerability feed.

learner202649/CVE-2026-42271-PoC (github)
HORKimhab/CVE-2026-42271 (github)

Affected products and versions

BerriAI: litellm

How to fix CVE-2026-42271

The record marks a vendor fix as available for CVE-2026-42271. Patch reference: https://github.com/BerriAI/litellm/security/advisories/GHSA-v4p8-mg3p-g94g. Vendor advisory: https://github.com/BerriAI/litellm/security/advisories/GHSA-v4p8-mg3p-g94g. Because CVE-2026-42271 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-06-22. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2026-42271

4 tracked threats in the Threadlinqs corpus reference CVE-2026-42271, either in the campaign’s CVE list or as an indicator on the campaign record.

GTIG: AI-Era Vulnerability Discovery and Exploitation Surge — In-the-Wild Exploitation of BeyondTrust CVE-2026-1731, LiteLLM CVE-2026-42271 and Langflow CVE-2026-5027 — CRITICAL · 2026-09-30
Qilin-Linked Campaign Exploits MCP Gateway and LLM Framework Flaws (CVE-2026-59822, CVE-2026-42271, CVE-2026-48710) for RCE and Cryptomining — CRITICAL · 2026-08-28
CVE-2026-42271: LiteLLM AI Gateway OS Command Injection via MCP Test Endpoints, Chained to Unauthenticated RCE with CVE-2026-48710 (CISA KEV, Active Exploitation) — CRITICAL · 2026-06-09
CVE-2026-42271: LiteLLM MCP Server Command Injection Under Active Exploitation, Chained with CVE-2026-48710 (Starlette BadHost) for Unauthenticated RCE — CRITICAL · 2026-06-09

Sources

Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-09-30. This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

github.com

Other references

github.com

Full detection coverage & IOCs for threats exploiting CVE-2026-42271 are available via the Threadlinqs MCP server (Purple tier). View plans →

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