{"cve":"CVE-2025-62800","nvd":{"published":"2025-10-28T22:15:36.983","modified":"2026-10-08T11:10:00.250","status":"Analyzed","description":"FastMCP is the standard framework for building MCP applications. Versions prior to 2.13.0 have a reflected cross-site scripting vulnerability in the OAuth client callback page (oauth_callback.py) where unescaped user-controlled values are inserted into the generated HTML, allowing arbitrary JavaScript execution in the callback server origin. The issue is fixed in version 2.13.0.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","score":5.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","score":6.1},"cwes":["CWE-79"],"references":["https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc","https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc"],"products":["jlowin:fastmcp"],"source":"nvd","synced_at":"2026-10-19T22:14:53.307938015+00:00"},"epss":{"cve":"CVE-2025-62800","score":0.00276,"percentile":0.19859,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-mxxr-jv3v-6pgc","url":"https://osv.dev/vulnerability/GHSA-mxxr-jv3v-6pgc","summary":"FastMCP vulnerable to reflected XSS in client's callback page","modified":"2026-07-07T17:56:05.411756133Z","packages":[{"ecosystem":"PyPI","name":"fastmcp","purl":"pkg:pypi/fastmcp","ranges":["<2.13.0"],"fixed":["2.13.0"]}]},{"id":"PYSEC-2026-1364","url":"https://osv.dev/vulnerability/PYSEC-2026-1364","summary":"FastMCP vulnerable to reflected XSS in client's callback page","modified":"2026-07-07T17:47:12.914598102Z","packages":[{"ecosystem":"PyPI","name":"fastmcp","purl":"pkg:pypi/fastmcp","ranges":["<2.13.0"],"fixed":["2.13.0"]}]}],"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."]}