---
id: CVE-2026-45018
title: >-
  Chainlit is a Python framework for building production-ready conversational AI
  applications
summary: >-
  Chainlit is a Python framework for building production-ready conversational AI
  applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with
  features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp
  endpoint wi…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-78
vendor: chainlit
product: chainlit
affected:
  - 'chainlit >= 2.4.0rc0, <= 2.11.1'
patched:
  - chainlit 2.12.0
published: '2026-08-25'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:07:31.353'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-45018'
references:
  - url: >-
      https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-001--command-injection-via-mcp-stdio
    label: security-advisories@github.com
  - url: >-
      https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9
    label: security-advisories@github.com
  - url: 'https://github.com/Chainlit/chainlit/releases/tag/2.12.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j
    label: security-advisories@github.com
  - url: >-
      https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-w3fx-mc44-mf6j'
  - url: 'https://github.com/Chainlit/chainlit'
  - url: 'https://pypi.org/project/chainlit'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-45018'
tags:
  - nvd
  - ghsa
  - pip
  - osv
epss: 0.00653
epssPercentile: 0.4989
aliases:
  - GHSA-w3fx-mc44-mf6j
  - PYSEC-2026-3812
ecosystem: pip
ingestedAt: '2026-08-25T19:31:03.133Z'
---

## Overview

Chainlit is a Python framework for building production-ready conversational AI applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp endpoint without requiring authentication. For stdio transport, the endpoint accepts a user-controlled fullCommand string. The validate_mcp_command() function in backend/chainlit/mcp.py checks only the executable name against config.features.mcp.stdio.allowed_executables and passes unchecked arguments to StdioServerParameters in backend/chainlit/server.py. Because npx supports the -c argument, an attacker can execute arbitrary shell commands with the privileges of the Chainlit process. If allowed_executables is unset, its None default is treated as allowing every executable. This issue is fixed in version 2.12.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-45018)

Affected packages:

- `chainlit >= 2.4.0rc0, <= 2.11.1`

Patched in:

- `chainlit 2.12.0`

Source: https://github.com/advisories/GHSA-w3fx-mc44-mf6j