SSRF in Chainlit
CVE-2026-120492
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.
Vulnerability class: SSRF (Server-Side Request Forgery)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Chainlit — versions 2.12.0
Weakness classification (CWE)
References
- github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j (vendor-advisory)
- github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py (technical-description)
- github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py (technical-description)
- www.vulncheck.com/advisories/chainlit-2.12.0-ssrf-via-semicolon-path-segment-in… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-120492?
- CVE-2026-120492 is a medium-severity vulnerability in Chainlit, classified under Server-Side Request Forgery (SSRF). CVSS score: 5.4/10. Published 2026-11-02.
- How severe is CVE-2026-120492?
- Medium severity. CVSS v3 base score is 5.4 out of 10.