{"cve":"CVE-2026-27124","nvd":{"published":"2026-04-03T16:16:36.453","modified":"2026-07-24T22:10:00.140","status":"Analyzed","description":"FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, while testing the GitHubProvider OAuth integration, which allows authentication to a FastMCP MCP server via a FastMCP OAuthProxy using GitHub OAuth, it was discovered that the FastMCP OAuthProxy does not properly validate the user's consent upon receiving the authorization code from GitHub. In combination with GitHub’s behavior of skipping the consent page for previously authorized clients, this introduces a Confused Deputy vulnerability. This issue has been patched in version 3.2.0.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","score":8.2},"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-441"],"references":["https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733","https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733"],"products":["jlowin:fastmcp"],"source":"nvd","synced_at":"2026-10-19T22:28:59.047572785+00:00"},"epss":{"cve":"CVE-2026-27124","score":0.00211,"percentile":0.11362,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-rww4-4w9c-7733","url":"https://osv.dev/vulnerability/GHSA-rww4-4w9c-7733","summary":"FastMCP: Missing Consent Verification in OAuth Proxy Callback Facilitates Confused Deputy Vulnerabilities","modified":"2026-09-10T03:50:40.968939735Z","packages":[{"ecosystem":"PyPI","name":"fastmcp","purl":"pkg:pypi/fastmcp","ranges":["<3.2.0"],"fixed":["3.2.0"]}]},{"id":"PYSEC-2026-2476","url":"https://osv.dev/vulnerability/PYSEC-2026-2476","summary":"FastMCP: Missing Consent Verification in OAuth Proxy Callback Facilitates Confused Deputy Vulnerabilities","modified":"2026-07-13T16:31:55.205498605Z","packages":[{"ecosystem":"PyPI","name":"fastmcp","purl":"pkg:pypi/fastmcp","ranges":["<3.2.0"],"fixed":["3.2.0"]}]}],"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."]}