What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-28 · updated 2026-10-24
• Weakness: CWE-476

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 products

• github-mcp-server: before 1.1.0 — fixed in 1.1.0

How to fix

Upgrade to a fixed version: github-mcp-server 1.1.0. Check the vendor advisory for mitigations.

References

• 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/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

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