{"apiVersion":"1.0","identifier":"CVE-2026-45019","description":"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.","publishedAt":"2026-08-25T20:16:55","lastModifiedAt":"2026-08-27T17:18:24","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-45019","cvssScore":7.2,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N","epssProbability":0.00319,"riskScore":0.74,"affectedProduct":"Chainlit","affectedVersions":">=2.4.0rc0,<2.12.0","vulnerabilityType":"Library","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-45019","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-45019","en":"https://www.redsauce.net/en/cves/CVE-2026-45019","fr":"https://www.redsauce.net/fr/cves/CVE-2026-45019","pt":"https://www.redsauce.net/pt/cves/CVE-2026-45019","de":"https://www.redsauce.net/de/cves/CVE-2026-45019","sk":"https://www.redsauce.net/sk/cves/CVE-2026-45019","el":"https://www.redsauce.net/el/cves/CVE-2026-45019"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-45019"}}