CVE-2026-61559

The @zereight/mcp-gitlab MCP server (repository zereight/gitlab-mcp) is vulnerable to server-side request forgery (CWE-918) when the environment variable ENABLE_DYNAMIC_API_URL=true is set: the server honors an attacker-supplied X-GitLab-API-URL request header as the base URL for all outbound GitLab API calls, validating only URL syntax with no allowlist or hostname restriction. Because the server attaches the victim's GitLab Private-Token to every outbound fetch using that redirected URL, any caller who can reach the HTTP/SSE transport can point the server at an attacker-controlled host and capture the victim's token, giving full access to whatever GitLab projects and permissions that token grants. All versions through commit 74a8c83 are affected, and no patched version was available at the time of the report. The flaw is rated critical (CVSS 3.1 9.6; the advisory text also cites 8.5) and the report includes a working proof-of-concept, though no exploitation in the wild is known and it is not on the CISA KEV list.

What to do: Do not set ENABLE_DYNAMIC_API_URL=true; leave the dynamic API URL feature disabled (its default state) until a patched release is published. If the flag was ever enabled on a network-reachable instance, rotate the configured GitLab private tokens immediately and review logs for outbound requests to unexpected hosts carrying private-token headers. Restrict access to the MCP HTTP/SSE endpoints (bind to localhost, firewall the port, require strong authentication) and monitor the upstream repository for a fix.