# CVE-2026-47427: GitHub MCP Server denial of service via nil pointer dereference in CompletionsHandler

Source: https://junglewise.ai/threats/cve-2026-47427-github-mcp-server-denial-of-service-via-nil-pointer-dereference  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-28. Updated: 2026-07-28  
License: CC BY 4.0 with a link back

CVE-2026-47427 · Severity: high · CVSS 7.5 · Published 2026-07-28

GitHub MCP Server is a tool used to integrate GitHub data and functionality with AI models. A flaw in how the server handles specific requests allows an unauthenticated attacker to crash the service by sending a specially crafted message. This results in a total denial of service, preventing the AI tools from accessing GitHub data until the server is manually restarted.

Vendors: [GitHub](https://junglewise.ai/threats/vendors/github), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-47427 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47427 being exploited in the wild.

**How severe is CVE-2026-47427?** High severity, with a CVSS score of 7.5, published 28 July 2026.

**Which products and versions are affected?** Github-Mcp-Server < 1.1.0; github.com/github/github-mcp-server (Go) < 1.1.0, SEMVER:introduced=0,fixed=1.1.0.

**Is there a fix for CVE-2026-47427?** Yes. github.com/github/github-mcp-server (Go): upgrade to 1.1.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47427 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-47427?** Check whether you run Github-Mcp-Server or github.com/github/github-mcp-server (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/github/github-mcp-server (Go): upgrade to 1.1.0 or later

  ```sh
  go get github.com/github/github-mcp-server@v1.1.0
  ```


## Technical details

A vulnerability exists in the `CompletionsHandler` function within `pkg/github/server.go` of the GitHub MCP Server. The function attempts to access `params.Ref` without verifying if the pointer is nil. An attacker can trigger a Go runtime panic by sending a `completion/complete` JSON-RPC request that omits the `ref` field or contains empty parameters. Because this dereference occurs before authentication or token validation, any network-reachable client can crash the process. The issue is resolved in version 1.1.0 by implementing proper nil-guards on the request parameters.

## Affected products

- GitHub github-mcp-server < 1.1.0

## Identifiers

- CVE-2026-47427
- GHSA-w4q6-qw23-4rg7
- GO-2026-6118

## Timeline

- 2026-02-21: disclosed: Initial report to GitHub Open Source Security
- 2026-05-19: patched: Fix merged into main branch
- 2026-05-28: patched: Version 1.1.0 released
- 2026-07-20: advisory: GitHub Security Advisory published
- 2026-07-28: advisory: NVD published CVE-2026-47427

## References

- [https://github.com/github/github-mcp-server/commit/c88d2ecdd3bb07f7bdd75296e3ee676febf14f58](https://github.com/github/github-mcp-server/commit/c88d2ecdd3bb07f7bdd75296e3ee676febf14f58)
- [https://github.com/github/github-mcp-server/pull/2502](https://github.com/github/github-mcp-server/pull/2502)
- [https://github.com/github/github-mcp-server/releases/tag/v1.1.0](https://github.com/github/github-mcp-server/releases/tag/v1.1.0)
- [https://github.com/github/github-mcp-server/security/advisories/GHSA-w4q6-qw23-4rg7](https://github.com/github/github-mcp-server/security/advisories/GHSA-w4q6-qw23-4rg7)

## Related threats

- [GitHub MCP Server improper access control in lockdown mode](https://junglewise.ai/threats/cve-2026-48529-github-mcp-server-improper-access-control-in-lockdown-mode)