CVE-2026-45019 json
Chainlit: SSRF via MCP SSE and streamable-http transports allows unauthenticated internal network access
published 2026-08-25 2 mo ago modified 2026-11-03 6 d ago also CVE-2026-120492 , GHSA-hvfh-5mj3-5f3j , PYSEC-2026-3811 , EUVD-2026-65738
- 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
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2 mo ago
Exploit prediction
0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-08).
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 |
| OSV | 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 |
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
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