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

Advisory record · `GHSA-w3fx-mc44-mf6j`

- **Identifiers:** `GHSA-w3fx-mc44-mf6j` · `CVE-2026-45018` · `PYSEC-2026-3812`
- **State:** Confirmed
- **Severity:** CVSS 9.8 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-78](https://cwe.mitre.org/data/definitions/78.html)
- **Tags:** [Command injection](https://agentprime.io/advisories/tag/command-injection.md)
- **Published:** 25 Aug 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

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.

## Critical

Critical, because:

- CVSS score 9.8: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `chainlit` (PyPI): affected `>=2.4.0rc0, <2.12.0`; fixed in `2.12.0`

## 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

- 9.8 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`, from 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

- 31 Oct 2026, 14:10 UTC: First seen by agentprime
- 31 Oct 2026, 14:10 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-w3fx-mc44-mf6j)

## Sources

- [GitHub Advisory Database: GHSA-w3fx-mc44-mf6j](https://github.com/advisories/GHSA-w3fx-mc44-mf6j)
- [OSV: GHSA-w3fx-mc44-mf6j](https://osv.dev/vulnerability/GHSA-w3fx-mc44-mf6j)
- <https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j>
- <https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9>
- <https://github.com/Chainlit/chainlit>
- <https://github.com/Chainlit/chainlit/releases/tag/2.12.0>

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.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-w3fx-mc44-mf6j>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-w3fx-mc44-mf6j/>. Everything for agents: <https://agentprime.io/llms.txt>.