{"id":"CVE-2026-44429","revision":"e7def23607124ba7ac528748df0b990d","records":[{"revision":"e7def23607124ba7ac528748df0b990d","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-44429","aliases":[],"title":"MCP Registry: Stored XSS in catalogue UI via attribute-quote breakout in publisher-controlled `websiteUrl`","description":"The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.7, the public catalogue UI served at GET / (file internal/api/handlers/v0/ui_index.html) is vulnerable to stored cross-site scripting via the server.websiteUrl field of any published server.json. Server-side validation in internal/validators/validators.go (validateWebsiteURL) only checks that the URL parses, is absolute, and uses the https scheme; it does not reject quote characters. Client-side, the value is interpolated into a double-quoted href attribute via innerHTML, using a homegrown escapeHtml helper that performs the standard textContent → innerHTML round-trip. Per the HTML serialisation algorithm, that round-trip encodes only &, <, > and U+00A0 inside text nodes — it does not encode \" or '. A literal \" in websiteUrl therefore breaks out of the href attribute, allowing arbitrary on* event handlers to be appended to the same <a> element. The Content-Security-Policy on / is script-src 'self' 'unsafe-inline' https://cdn.tailwindcss.com, so the injected event handlers execute. Any user able to obtain a publish token (e.g. via POST /v0/auth/github-at with their own GitHub account, or POST /v0/auth/none on a deployment that has anonymous auth enabled) can plant a poisoned record visible to every visitor of the registry homepage. This vulnerability is fixed in 1.7.7.","state":0,"publishedAt":"2026-05-14T21:05:56.13+00:00","modifiedAt":"2026-05-15T14:20:27.564+00:00","affected":[{"ecosystem":"Vendor product","name":"registry","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"modelcontextprotocol\",\n                    \"product\": \"registry\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 1.7.7\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:L","score":5.1,"severity":"MEDIUM"}],"references":["https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-rqv2-m695-f8j4"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-44429","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-44429","identifiers":["CVE-2026-44429"]},"retained":false,"historicalAffected":[]}],"coverage":[]}