CVE-2026-47427 GitHub MCP Server: Nil Pointer Dereference DoS in completion/complete Handler
Unauthenticated attackers can crash the GitHub MCP Server by sending a malformed completion request, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-47427?
CVE-2026-47427 is a high-severity vulnerability in github-mcp-server, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-476
Which versions are affected by CVE-2026-47427?
3 open source packages ship an affected version, including github.com/github/github-mcp-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/github/github-mcp-server Go | All versions | 1.1.0 |
github.com/github/github-mcp-server Go | All versions | 1.1.0 |
github.com/github/github-mcp-server Go | All versions | 1.1.0 |
Products include Github Mcp Server.
How do I fix CVE-2026-47427?
Upgrade github.com/github/github-mcp-server to 1.1.0 or later.
Is CVE-2026-47427 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47427 exists.
Sources
Also known as GHSA-w4q6-qw23-4rg7, GO-2026-6118.