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

Summary A nil pointer dereference vulnerability in the GitHub MCP Server causes it to crash when receiving a malformed completion/complete request with missing or empty parameters. This allows any unauthenticated client…

7.5CVSS Score

HIGHSeverity

NOCISA KEV

VulnerabilityImpact Type

📋 Vulnerability Details

CVE ID	CVE-2026-47427
Vendor	go
Affected Product	github.com/github/github-mcp-server
Vulnerability Type	Vulnerability
CVSS Score	7.5 (HIGH)
Actively Exploited	❌ No known exploitation
Patch Status	See Vendor Advisory →
Reported By	CYBERDUDEBIVASH SENTINEL APEX Intelligence (via github_advisories)

🔬 Technical Analysis

Summary A nil pointer dereference vulnerability in the GitHub MCP Server causes it to crash when receiving a malformed `completion/complete` request with missing or empty parameters. This allows any unauthenticated client to cause a complete denial of service.

Details The `CompletionsHandler` function in `pkg/github/server.go:198` accesses `params.Ref` without checking if it's nil first. When a client sends a `completion/complete` request with a missing `ref` field, the handler dereferences nil and the Go runtime panics. The crash occurs before any authentication or token validation, so even requests with fake tokens can trigger it.

PoC After completing the MCP initialization handshake, send either: Empty params: {"jsonrpc":"2.0","id":2,"method":"completion/complete","param

📚 Advisory References

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