CVE Explorer

CVE-2026-27124

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

Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:101442d7cb88f27fcd4bb9ef7194850e913e4ed1e1b86bbec2b13cc170dfb634

Known exploited

Not asserted

Disputed

Stale source

Conflicts

Affected products and versions

1 source assertion

{"product":"fastmcp","vendor":"jlowin","versions":[{"status":"affected","version":"< 3.2.0"}]}

cve_program_cvelist_v5affected
urn:baitaphish:normalized-source-record:v2:b664a520071789d9f6a375188967a4b7704f830ab6a72cabfe8a3b8ac5f1d20d · sha256:8711d026522e7869… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion

{"metric":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":8.2,"baseSeverity":"HIGH","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH"},"metric_type":"cvssV4_0"}

cve_program_cvelist_v5cvss
urn:baitaphish:normalized-source-record:v2:b664a520071789d9f6a375188967a4b7704f830ab6a72cabfe8a3b8ac5f1d20d · sha256:8711d026522e7869… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

1 source assertion

{"cweId":"CWE-441","description":"CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:b664a520071789d9f6a375188967a4b7704f830ab6a72cabfe8a3b8ac5f1d20d · sha256:8711d026522e7869… · /containers/cna/problemTypes/0/descriptions/0

Source references

2 source assertions

{"tags":["exploit"],"url":"https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733"}

cve_program_cvelist_v5reference
urn:baitaphish:normalized-source-record:v2:b664a520071789d9f6a375188967a4b7704f830ab6a72cabfe8a3b8ac5f1d20d · sha256:8711d026522e7869… · /containers/adp/0/references/0

{"name":"https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733","tags":["x_refsource_CONFIRM"],"url":"https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733"}

cve_program_cvelist_v5reference
urn:baitaphish:normalized-source-record:v2:b664a520071789d9f6a375188967a4b7704f830ab6a72cabfe8a3b8ac5f1d20d · sha256:8711d026522e7869… · /containers/cna/references/0

Attribution and limitations

CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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