GO-2026-6911

    Dashboard / Vulnerabilities / GO-2026-6911

    GO-2026-6911

    Published: 5 Nov 2026Last Modified: 5 Nov 2026

    Summary: SSRF and credential leak via unvalidated Location header in github.com/mark3labs/mcp-go

    Details: In github.com/mark3labs/mcp-go/client/transport, NewStreamableHTTP constructs an http.Client with a nil CheckRedirect policy when no custom WithHTTPBasicClient is supplied, and attaches static custom headers and OAuth bearer tokens inside a RoundTripper layer. If an MCP server responds with a 3xx redirect, the client follows the Location header to arbitrary hosts and schemes and attaches configured WithHeaders and OAuth Authorization headers to the redirected request, enabling server-side request forgery (SSRF) and credential disclosure.

    References: https://github.com/golang/vulndb/issues/6911, https://github.com/mark3labs/mcp-go/issues/1164

    Affected packages

    Package

    Name: github.com/mark3labs/mcp-go

    Purl: pkg:golang/github.com/mark3labs/mcp-go

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -None

    Affected versions

    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
    GO-2026-6911 | CVE-DB