{"id":"CVE-2025-62800","state":"PUBLISHED","title":"FastMCP vulnerable to reflected XSS in client's callback page","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.","publishedAt":"2025-10-28T21:34:40.392Z","updatedAt":"2025-10-29T15:52:44.433Z","severity":{"score":5.3,"label":"Medium","version":"4.0","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","source":"GitHub_M"},"assigner":"GitHub_M","products":["jlowin fastmcp"],"affected":[{"vendor":"jlowin","product":"fastmcp","versions":[{"version":"< 2.13.0","status":"affected"}]}],"references":["https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc"],"weaknesses":["CWE-79"],"ingestedAt":"2026-10-29T20:09:48.677Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/62xxx/CVE-2025-62800.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-62800","state":"PUBLISHED","datePublished":"2025-10-28T21:34:40.392Z","dateUpdated":"2025-10-29T15:52:44.433Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2025-10-22T18:55:48.012Z"},"containers":{"cna":{"title":"FastMCP vulnerable to reflected XSS in client's callback page","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"jlowin","product":"fastmcp","versions":[{"version":"< 2.13.0","status":"affected"}]}],"references":[{"url":"https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc","name":"https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc","tags":["x_refsource_CONFIRM"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","subAvailabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-79","lang":"en","description":"CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2025-10-28T21:34:40.392Z"},"source":{"advisory":"GHSA-mxxr-jv3v-6pgc","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2025-10-29T15:52:40.720132Z","id":"CVE-2025-62800","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-10-29T15:52:44.433Z"}}]}}}