Medium severity5.4NVD Advisory· Published Nov 2, 2026· Updated Nov 2, 2026
CVE-2026-120492
CVE-2026-120492
Description
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.
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Affected products
1Patches
Vulnerability mechanics
References
4- github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.pynvd
- github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.pynvd
- github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3jnvd
- www.vulncheck.com/advisories/chainlit-2.12.0-ssrf-via-semicolon-path-segment-in-mcp-allowed-urlsnvd
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