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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-27124 Detail

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.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
CVSS-B 8.2 HIGH
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

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733 CISA-ADP, GitHub, Inc. Exploit  Mitigation  Vendor Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-441 Unintended Proxy or Intermediary ('Confused Deputy') GitHub, Inc.  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

6 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-27124
NVD Published Date:
04/03/2026
NVD Last Modified:
07/24/2026
Source:
GitHub, Inc.