{"id":"GHSA-v8vw-gw5j-w7m6","summary":"MCP Registry has open redirect via protocol-relative path in trailing-slash middleware","details":"### Summary\nThe TrailingSlashMiddleware in internal/api/server.go is vulnerable to an open redirect attack. An attacker can craft a URL with a protocol-relative path (e.g., //evil.com/) that, after trailing slash removal, results in a Location header of //evil.com — which browsers interpret as an absolute URL to an external domain.\n\n### Details\nThe TrailingSlashMiddleware strips trailing slashes from request paths and issues a 308 Permanent Redirect to the cleaned path. However, it does not validate or sanitize the resulting path before using it as the redirect target.\n\nWhen a request is made with a path like //evil.com/, the middleware processes it as follows:\n\n### PoC\n1. Start the registry server locally or identify a deployed instance\n2. Send a request with a double-slash path followed by an external domain:\n`curl -v https://\u003cregistry-host\u003e//evil.com/`\n\u003cimg width=\"3066\" height=\"969\" alt=\"image\" src=\"https://github.com/user-attachments/assets/a5305f00-29bf-4708-952a-478d608f2074\" /\u003e\n3. Observe the 308 Permanent Redirect response with Location: //evil.com:\n4. When accessed in a browser, the user is redirected to https://evil.com\n\n\n\n### Impact\n**Phishing**: Attackers can abuse the trusted registry domain to redirect users to credential-harvesting pages\n**Malware distribution**: Redirect users to sites serving malicious downloads\n**Trust abuse:** Links originating from the official MCP Registry domain carry implicit trust","aliases":["CVE-2026-44427","GO-2026-5658"],"modified":"2026-07-17T21:12:17.019178972Z","published":"2026-05-08T17:02:12Z","database_specific":{"github_reviewed_at":"2026-05-08T17:02:12Z","nvd_published_at":"2026-05-14T22:16:44Z","cwe_ids":["CWE-601"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-v8vw-gw5j-w7m6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44427"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/registry/pull/1227"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/registry/commit/1201cbd82b2cf6d4b56edfc05c763059a12f9fdb"},{"type":"PACKAGE","url":"https://github.com/modelcontextprotocol/registry"},{"type":"WEB","url":"https://github.com/modelcontextprotocol/registry/releases/tag/v1.7.5"}],"affected":[{"package":{"name":"github.com/modelcontextprotocol/registry","ecosystem":"Go","purl":"pkg:golang/github.com/modelcontextprotocol/registry"},"ranges":[{"type":"SEMVER","events":[{"introduced":"1.1.0"},{"fixed":"1.7.5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-v8vw-gw5j-w7m6/GHSA-v8vw-gw5j-w7m6.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P"}]}