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CVE-2026-120492 Details

ANALYZED

This CVE record has been analyzed and enriched by NVDAPI.com as an independent party.

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.

Metrics

CVSS 3.x Severity and Vector Strings:

VolerionCVSS-B:5.4 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:L

CNA: [email protected]CVSS-B:5.4 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j	CISA-ADP	AdvisoryBundleExploitRemedyVendor
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L199-L208	[email protected]	Source CodeVendor
https://github.com/Chainlit/chainlit/blob/2.12.0/backend/chainlit/mcp.py#L90-L177	[email protected]	Source CodeVendor
https://github.com/Chainlit/chainlit/security/advisories/GHSA-hvfh-5mj3-5f3j	[email protected]	AdvisoryBundleExploitRemedyVendor
https://www.vulncheck.com/advisories/chainlit-2.12.0-ssrf-via-semicolon-path-segment-in-mcp-allowed-urls	[email protected]	Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-918	Server-Side Request Forgery (SSRF)	[email protected]

Affected Products

Product	Versions
Chainlit	>= 2.4.0rc0, <= 2.11.1 >= 2.6.4, <= 2.11.1 (semver)
CPE No CPEs found in CPE dictionary for this product. Remediation Workaround:low effort Set `features.mcp.enabled = false` in `.chainlit/config.toml`. This fully prevents exploitation of this issue. Mitigation:low effort Restrict outbound network egress from the host running Chainlit (e.g., firewall rules blocking access to internal address ranges and the cloud metadata endpoint). Mitigation:low effort Configure authentication (register an auth callback) so that `/mcp` requires an authenticated session. This does not eliminate the SSRF for authenticated users, but removes the unauthenticated attack path.

Product

Versions

Chainlit

>= 2.4.0rc0, <= 2.11.1

>= 2.6.4, <= 2.11.1 (semver)

CPE

No CPEs found in CPE dictionary for this product.

Remediation

Workaround:low effort
Set `features.mcp.enabled = false` in `.chainlit/config.toml`. This fully prevents exploitation of this issue.
Mitigation:low effort
Restrict outbound network egress from the host running Chainlit (e.g., firewall rules blocking access to internal address ranges and the cloud metadata endpoint).
Mitigation:low effort
Configure authentication (register an auth callback) so that `/mcp` requires an authenticated session. This does not eliminate the SSRF for authenticated users, but removes the unauthenticated attack path.

Change History

2 change records found show changes

Date	Action	Recorded By
Nov 7, 2026	CVE Modified	CISA-ADP
Nov 2, 2026	New CVE Received	[email protected]