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High, CVSS 7.5amended

GitHub MCP Server has Nil Pointer Dereference DoS in completion/complete Handler

CVE-2026-47427GHSA-w4q6-qw23-4rg7

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/github/github-mcp-server 1.1.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-47427: 0.77% estimated exploitation activity in the next 30 days; percentile 55.72 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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","params":{}} Missing ref field: {"jsonrpc":"2.0","id":2,"method":"completion/complete","params":{"argument":{"name":"x","value":"y"}}} Result: panic: runtime error: invalid memory address or nil pointer dereference goroutine 42…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-w4q6-qw23-4rg7

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6118

  3. Revision 1 · created ·

    Published from osv record GHSA-w4q6-qw23-4rg7

Agent brief

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# Patch Next advisory brief: CVE-2026-47427

Advisory: GitHub MCP Server has Nil Pointer Dereference DoS in completion/complete Handler
IDs: CVE-2026-47427, GHSA-w4q6-qw23-4rg7
Record: https://patchnext.com/advisories/cve-2026-47427 (revision 3, source checked 26 Oct 2026, 15:27 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/github/github-mcp-server 1.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/github/github-mcp-server: affected < 1.1.0; fixed in 1.1.0

## Suggested inspection (read-only)
- Go github.com/github/github-mcp-server: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/github/github-mcp-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w4q6-qw23-4rg7 (OSV record GHSA-w4q6-qw23-4rg7 lists affected ranges: Go github.com/github/github-mcp-server >=0 <1.1.0 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6118 (OSV record GO-2026-6118 lists affected ranges: Go github.com/github/github-mcp-server >=0 <1.1.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w4q6-qw23-4rg7 (GitHub-reviewed advisory GHSA-w4q6-qw23-4rg7 lists affected ranges: Go github.com/github/github-mcp-server >=0 <1.1.0)

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