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    CVE-2026-123272

    Mark3labs mcp-go before v1.2.1 contains an improper validation vulnerability in OAuthHandler.fetchServerMetadata that allows malicious MCP servers to obtain tokens for other resources by declaring arbitrary resources in well-known metadata. Attackers can declare a different MCP server as the RFC 8707 resource indicator, causing the authorization server to mint tokens the attacker replays against that resource.

    Published:Nov 5, 2026
    Last Modified:Nov 5, 2026
    EPS:Nov 5, 2026
    EPSS Score:0.00196
    CVSS Score:8

    Affected Products

    Vendor
    Mark3labs
    Product
    Mcp-go

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-346 Origin Validation Error

    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
    CVE-2026-123272 — Mark3labs (Medium 5.1) | CVE-DB