Summary

GitHub CLI incorrectly includes authorization header in API requests to TUF repository mirrors via gh attestation, gh release verify, and gh release verify-asset commands.

Affected users:

• Authenticated github.com users who previously ran gh attestation commands, gh release verify, or gh release verify-asset: the github.com token was included in requests to tuf-repo.github.com, a GitHub Pages domain that is not a GitHub API endpoint. All authentication types are affected.
• Users with GH_ENTERPRISE_TOKEN or GITHUB_ENTERPRISE_TOKEN set who previously ran gh attestation commands, gh release verify, or gh release verify-asset: the enterprise token was included in requests to external hosts tuf-repo-cdn.sigstore.dev and tmaproduction.blob.core.windows.net. These hosts are not operated by GitHub.

Details

The CLI uses a shared HTTP client with an authentication layer that automatically attaches tokens to outgoing requests. This layer lacks accurate host detection and can incorrectly attribute the target host, providing it with a token it should never receive.

Specifically, the host normalization logic collapses any *.github.com subdomain to github.com, so a request to tuf-repo.github.com (a GitHub Pages site, not a GitHub API endpoint) is treated as a request to github.com and receives the user's github.com token. For hosts that don't match github.com or a known GHES instance at all, the resolver falls back to GH_ENTERPRISE_TOKEN if set.

The gh attestation, gh release verify and gh release verify-asset commands fetch data from several external hosts as part of their normal operation (TUF metadata from tuf-repo.github.com and tuf-repo-cdn.sigstore.dev, artifact bundles from Azure Blob Storage). Because these requests go through the same authenticated HTTP client, the token is sent to all of them.

Impact

Tokens were transmitted in HTTP headers to the listed hosts during normal gh attestation, gh release verify, and gh release verify-asset operations. We have no evidence that tokens were logged, retained, or accessed by unauthorized parties. If a token were captured, it would grant the same access as the token holder, potentially including private repositories, organization resources, or enterprise administration depending on token type and permissions.

Remediation and mitigation

1. Revoke authentication tokens used with the GitHub CLI:
   • Personal access tokens
   • GitHub CLI OAuth app
2. Upgrade gh to 2.93.0
3. Review your personal security log and any relevant audit logs for actions associated with your account or enterprise