GitHub Composer CVE-2026-45793: GITHUB_TOKEN Leaks to CI Logs via Regex Miss

What this error means

GitHub OAuth token contains invalid characters — Composer rejects GITHUB_TOKEN due to hyphen regex miss, exposing plaintext tokens in job logs is a GitHub Actions failure pattern reported for developers trying to fix github actions token leakage into ci logs caused by composer’s old regex rejecting new github_token format with hyphens. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Source: lilting.ch detailed analysis of CVE-2026-45793 disclosed May 13, 2026. Composer 2.3.0–2.9.7 rejected new GH Actions tokens containing hyphens (ghs__…), then embedded rejected token in exception messages written to stderr saved as job logs. Secret masking fails because ANSI color codes and line wrapping break contiguous string matching. Critical for paid Teams/Enterprise using setup-php or Composer in CI.

Common causes

• Source: lilting.ch detailed analysis of CVE-2026-45793 disclosed May 13, 2026. Composer 2.3.0–2.9.7 rejected new GH Actions tokens containing hyphens (ghs__…), then embedded rejected token in exception messages written to stderr saved as job logs. Secret masking fails because ANSI color codes and line wrapping break contiguous string matching. Critical for paid Teams/Enterprise using setup-php or Composer in CI.

Quick fixes

1. Confirm the exact error signature matches GitHub OAuth token contains invalid characters — Composer rejects GITHUB_TOKEN due to hyphen regex miss, exposing plaintext tokens in job logs.
2. Check the GitHub Actions account, local tool state, and provider configuration involved in the failing workflow.
3. Verify the account session, API key, provider settings, and environment where the failing tool is running.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://lilting.ch/en/articles/composer-github-actions-token-log-disclosure

Evidence note: Source: lilting.ch detailed analysis of CVE-2026-45793 disclosed May 13, 2026. Composer 2.3.0–2.9.7 rejected new GH Actions tokens containing hyphens (ghs__…), then embedded rejected token in exception messages written to stderr saved as job logs. Secret masking fails because ANSI color codes and line wrapping break contiguous string matching. Critical for paid Teams/Enterprise using setup-php or Composer in CI.

Related errors

• GitHub Actions

FAQ

What should I check first?

Start with the exact GitHub OAuth token contains invalid characters — Composer rejects GITHUB_TOKEN due to hyphen regex miss, exposing plaintext tokens in job logs text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed GitHub Actions workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without GitHub OAuth token contains invalid characters — Composer rejects GITHUB_TOKEN due to hyphen regex miss, exposing plaintext tokens in job logs.