CVE-2026-47427
Received Received - Intake

Denial of Service in GitHub MCP Server via Nil Pointer Dereference

Publication date: 2026-07-28

Last updated on: 2026-07-28

Assigner: GitHub, Inc.

Description
GitHub MCP Server is GitHub's official MCP Server. Prior to 1.1.0, the CompletionsHandler function in pkg/github/server.go accesses params.Ref without first checking whether it is nil, so a completion/complete request with a missing or empty ref field triggers a nil pointer dereference and a Go runtime panic; because the crash occurs before any authentication or token validation, any unauthenticated client able to send JSON-RPC messages can crash the server, resulting in a complete denial of service. This issue is fixed in version 1.1.0.

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Meta Information

Published
2026-07-28
Last Modified
2026-07-28
Generated
2026-07-28
AI Q&A
2026-07-28
EPSS Evaluated
N/A
NVD
CVE-2026-47427
EUVD
EUVD-2026-49875

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
github mcp_server 1.1.0
github github_mcp_server 1.1.0
github github_mcp_server to 1.1.0 (exc)
github github_mcp_server to 0.33.0 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.

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Executive Summary

CVE-2026-47427 is a nil pointer dereference vulnerability in the GitHub MCP Server affecting versions before 1.1.0. It occurs when the CompletionsHandler function accesses the params.Ref field without checking if it is nil. A malformed completion request with a missing or empty ref parameter causes the server to crash with a Go runtime panic before authentication or token validation, leading to a complete denial of service for any unauthenticated client sending JSON-RPC messages.

Detection Guidance

To detect this vulnerability, monitor for server crashes when processing completion requests. Check logs for nil pointer dereference errors or panics in the GitHub MCP Server. Use network traffic analysis to identify malformed JSON-RPC requests with missing or empty ref parameters.

Impact Analysis

This vulnerability allows any unauthenticated client to crash the GitHub MCP Server by sending a malformed request. This results in a complete denial of service, making the server unavailable for all users. The impact is high availability loss due to server crashes triggered by simple malformed input.

Compliance Impact

This vulnerability causes a denial of service by crashing the server through unauthenticated requests, which could disrupt services handling sensitive data. For GDPR, this may impact availability of personal data processing systems. For HIPAA, it could interrupt access to protected health information systems. The lack of authentication bypass also raises concerns about unauthorized access to regulated data environments.

Mitigation Strategies

Upgrade to GitHub MCP Server version 1.1.0 or later to apply the fix. If upgrading is not immediately possible, implement input validation to reject requests with missing or empty ref parameters before processing. Restrict unauthenticated access to the server if possible.

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