{"cve":"CVE-2026-44429","nvd":{"published":"2026-05-14T21:16:46.677","modified":"2026-10-26T14:10:00.130","status":"Analyzed","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.","cvss_v4":{"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},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","score":5.4},"cwes":["CWE-79","CWE-116"],"references":["https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-rqv2-m695-f8j4","https://github.com/modelcontextprotocol/registry/security/advisories/GHSA-rqv2-m695-f8j4"],"products":["lfprojects:mcp_registry"],"source":"nvd","synced_at":"2026-10-26T14:27:29.784594657+00:00"},"epss":{"cve":"CVE-2026-44429","score":0.00167,"percentile":0.05946,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-rqv2-m695-f8j4","url":"https://osv.dev/vulnerability/GHSA-rqv2-m695-f8j4","summary":"MCP Registry vulnerable to stored XSS in catalogue UI via attribute-quote breakout in publisher-controlled `websiteUrl`","modified":"2026-09-10T03:50:55.367821128Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/registry","purl":"pkg:golang/github.com/modelcontextprotocol/registry","ranges":["<1.7.7"],"fixed":["1.7.7"]}]},{"id":"GO-2026-5637","url":"https://osv.dev/vulnerability/GO-2026-5637","summary":"MCP Registry vulnerable to stored XSS in catalogue UI via attribute-quote breakout in publisher-controlled `websiteUrl` in github.com/modelcontextprotocol/registry","modified":"2026-06-25T23:01:36.340940916Z","packages":[{"ecosystem":"Go","name":"github.com/modelcontextprotocol/registry","purl":"pkg:golang/github.com/modelcontextprotocol/registry","ranges":["<1.7.7"],"fixed":["1.7.7"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}