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CVE-2026-120492NVD
Vulnerability Summary
Chainlit 2.12.0 contains a server-side request forgery vulnerability that allows unauthenticated attackers to bypass path-scoped MCP allowed_urls entries because validate_mcp_url does not reject the semicolon character. Attackers can submit MCP URLs with '..;' segments to the /mcp endpoint, causing requests to paths outside the operator's grant on origins that strip semicolon path parameters.
CVSS v4.0 Base Metrics — Score 6.3 (MEDIUM)
Attack VectorNetwork
Attack ComplexityLow
Attack RequirementsPresent
Privileges RequiredNone
User InteractionNone
Confidentiality (Vulnerable System)None
Integrity (Vulnerable System)None
Availability (Vulnerable System)None
Confidentiality (Subsequent System)Low
Integrity (Subsequent System)Low
Availability (Subsequent System)None
CVSS v3.1 Base Metrics — Score 5.4 (MEDIUM)
Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredNone
User InteractionNone
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone
Affected & Patched Versions
- Chainlit Chainlit >= 2.12.0
Not provided by cveorg for this CVE.
External References
- https://github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j
- https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L90-L177
- https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L199-L208
- https://www.vulncheck.com/advisories/chainlit-2.12.0-ssrf-via-semicolon-path-segment-in-mcp-allowed-urls