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Advisory record · GHSA-w3fx-mc44-mf6j

Chainlit has command injection via MCP stdio transport that allows unauthenticated remote code execution

CVSS 9.8 CriticalCriticalEPSS 0.011 · 65th percentile

Critical, because:

  • CVSS score 9.8: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 25 Aug 2026, 19:19 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
chainlitPyPI>=2.4.0rc0, <2.12.02.12.0
Identifiers
GHSA-w3fx-mc44-mf6j · CVE-2026-45018 · PYSEC-2026-3812
Weakness (CWE)
CWE-78
Tags
Published
25 Aug 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Chainlit versions >=2.4.0rc0 and <2.12.0 are vulnerable when features.mcp.enabled is set to true. An unauthenticated remote attacker can send a crafted command string to the MCP stdio endpoint, because the allowlist checks only the executable name and not its arguments, allowing arbitrary OS commands to run with the privileges of the Chainlit process. Upgrade to 2.12.0, which removes client-supplied commands. As a workaround, set features.mcp.enabled to false, which fully prevents exploitation of this issue.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.8 Critical 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.011, the 65th percentile, on 12 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:10 UTC First seen by agentprime
  2. 31 Oct 2026, 14:10 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.