{
  "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-hvfh-5mj3-5f3j"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-918"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45019.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 sse and streamable-http transports, ConnectSseMCPRequest and ConnectStreamableHttpMCPRequest in backend/chainlit/types.py accept a user-controlled url and optional headers dictionary without scheme validation, private-address filtering, or an allowlist. The connect_mcp handler in backend/chainlit/server.py passes these values to sse_client() or streamablehttp_client(), allowing the Chainlit server to make blind outbound requests to arbitrary internal or external services, including cloud metadata endpoints, with attacker-controlled Authorization and Cookie headers. The SSE URL sink has existed since 2.4.0rc0, while attacker-controlled header forwarding and streamable-http support were added in 2.6.4. The response is consumed internally and not returned, but the attacker can issue state-changing authenticated requests, discover internal services, scan ports, and probe metadata endpoints. This issue is fixed in version 2.12.0.",
  "id": "CVE-2026-45019",
  "modified": "2026-08-29T03:30:45.238124479Z",
  "published": "2026-08-25T19:20:59.339Z",
  "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-2026-45019.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-002--ssrf-via-mcp-streamable-http--sse"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45019"
    },
    {
      "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:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Chainlit: SSRF via MCP SSE and streamable-http transports allows unauthenticated internal network access"
}