CVE-2026-45019 json
Chainlit: SSRF via MCP SSE and streamable-http transports allows unauthenticated internal network access
published 2mo ago modified 6d ago also CVE-2026-120492 , EUVD-2026-65738 , GHSA-hvfh-5mj3-5f3j , PYSEC-2026-3811
- cvss
- 7.2
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 37%
- public exploits
- 0
- none known
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 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.
Patch / fix
- pypi chainlit 2.12.0
- chainlit chainlit 2.12.0
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Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2mo ago
Exploit prediction
0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| GitHub | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| OSV | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | chainlit | >=2.4.0rc0, <2.12.0 |
2.12.0 |
Affected products
- Chainlit chainlit
Classification
- Weakness
-
- CWE-918 Server-Side Request Forgery
References
-
github.com
/Chainlit/chainlit/commit/0565fd0eccb915fce159929598b053ed79f6e0c9
web
-
github.com
/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j
web
-
github.com
/Chainlit/chainlit/blob/2.12.0/docs/security-advisory-2026-mcp.md#spl-2026-002--ssrf-via-mcp-streamable-http--
web
-
github.com
/Chainlit/chainlit/releases/tag/2.12.0
web
-
github.com
/Chainlit/chainlit
package
-
pypi.org
/project/chainlit
package
-
github.com
/advisories/GHSA-hvfh-5mj3-5f3j
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-45019
advisory
Sources
- CVE List CVE-2026-45019
- GitHub Advisory GHSA-hvfh-5mj3-5f3j
- NVD CVE-2026-45019
- OSV PYSEC-2026-3811
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.