Vulnerability · Published Jul 28, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity null pointer dereference in github-mcp-server from github. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.8%top 44.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Go	github.com/github/github-mcp-server	1.1.0	GHSA-w4q6-qw23-4rg7
Go	github.com/github/github-mcp-server	1.1.0	GO-2026-6118

Affected products (as reported)

Vendor	Product	Versions
github	github-mcp-server	< 1.1.0

Weakness: CWE-476 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

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