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    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 Confused Deputy vulnerability. This issue has been patched in version 3.2.0.

    Published:Apr 3, 2026
    Last Modified:Apr 22, 2026
    EPS:Apr 3, 2026
    EPSS Score:0.00079
    CVSS Score:6.1

    Affected Products

    Vendor
    Jlowin
    Product
    Fastmcp

    Exploits

    https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733https://github.com/PrefectHQ/fastmcp/security/advisories/GHSA-rww4-4w9c-7733

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High