{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.4.0rc0"
              },
              {
                "fixed": "2.12.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "dc13fc0c858ce65814b685ee39dc112a3bd38c87"
            },
            {
              "fixed": "0565fd0eccb915fce159929598b053ed79f6e0c9"
            }
          ],
          "repo": "https://github.com/chainlit/chainlit",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-w3fx-mc44-mf6j"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-78"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45018.json"
  },
  "details": "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.",
  "id": "CVE-2026-45018",
  "modified": "2026-08-29T03:30:19.263017381Z",
  "published": "2026-08-25T19:18:46.439Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Chainlit/chainlit/releases/tag/2.12.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45018.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-001--command-injection-via-mcp-stdio"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Chainlit/chainlit/security/advisories/GHSA-w3fx-mc44-mf6j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45018"
    },
    {
      "type": "FIX",
      "url": "https://github.com/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Chainlit: Command injection via MCP stdio transport allows unauthenticated remote code execution"
}