Server-Side Request Forgery in Chainlit 2.12.0 by Chainlit
CVE-2026-120492

6.3MEDIUM

Key Information:

Vendor

Chainlit

Status
Chainlit
Vendor
CVE Published:
2 November 2026

What is CVE-2026-120492?

Chainlit version 2.12.0 is affected by a server-side request forgery vulnerability that enables unauthenticated attackers to exploit the '/mcp' endpoint. The flaw arises from the failure to properly validate MCP URLs, allowing the inclusion of semicolon characters in the path. This oversight can lead to a bypass of the defined path-scoped MCP allowed_urls entries, permitting requests to unauthorized paths. Attackers can manipulate MCP URLs with '..;' segments to access resources beyond the intended restrictions, potentially compromising the security and integrity of the affected systems.

Affected Version(s)

Chainlit 2.12.0

References

https://github.com/Chainlit/chainlit/security/advisories/...
vendor-advisory
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/...
technical-description
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/...
technical-description

CVSS V4

Score:
6.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Gavin Blacklock
.