GO-2026-6911

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Source

https://pkg.go.dev/vuln/GO-2026-6911

Import Source

https://vuln.go.dev/ID/GO-2026-6911.json

JSON Data

https://api.osv.dev/v1/vulns/GO-2026-6911

Published

2026-11-05T22:55:15Z

Modified

2026-11-05T23:15:16Z

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.

Database specific

{
    "review_status": "REVIEWED",
    "url": "https://pkg.go.dev/vuln/GO-2026-6911"
}

References

Credits

- kanywst

Affected packages

Go / github.com/mark3labs/mcp-go

Package

Name: github.com/mark3labs/mcp-go; View open source insights on deps.dev
Purl: pkg:golang/github.com/mark3labs/mcp-go

Affected ranges

Type: SEMVER
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Ecosystem specific

{
    "imports": [
        {
            "path": "github.com/mark3labs/mcp-go/client/transport",
            "symbols": [
                "NewStreamableHTTP",
                "StreamableHTTP.Close",
                "StreamableHTTP.SendNotification",
                "StreamableHTTP.SendRequest",
                "StreamableHTTP.SetRequestHandler"
            ]
        }
    ]
}

Database specific

source

"https://vuln.go.dev/ID/GO-2026-6911.json"