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CriticalVulnerabilityCVE-2026-118762updated 29 Oct 2026, 17:20 UTC

Monkeytype CI workflow lets outside code steal repository write access

A build check in the typing-test project's automation could let an outsider run their own code with the project's own access key. That key could be used to change the project's code or its pull requests and issues.

Fixed in 26.43.0Official source
SeverityCriticalCVSS 9.3 of 10
Being exploited?UnclearNo reports either way yet
Fix available?Yes26.43.0 · since 29 Oct 2026
How sure is this?Official sourceBacked by an official source

How the attack works simplified

  1. 1Outside contributorOpens pull request from a fork
  2. 2Format label appliedWorkflow triggers on pull_request_target
  3. 3Fork code runsInstalls fork dependencies and runs its oxfmt
  4. 4Token exposedGITHUB_TOKEN left in git config
  5. 5Repository changedAttacker pushes content or edits PRs and issues
  6. ResultAttacker gains repository write access

What happened

The fix-formatting.yml GitHub Actions workflow runs on pull_request_target with write permissions, checks out a fork PR, installs its dependencies, and executes the fork's oxfmt binary, while actions/checkout leaves the GITHUB_TOKEN in git config before untrusted code runs.

Why it is dangerous: An external contributor whose pull request gets the format label can execute arbitrary code, read or exfiltrate the GITHUB_TOKEN, and push content or modify pull requests and issues in the repository. The Monkeytype application and user data are not affected.

Are you affected?

You are affected if you run the Monkeytype repository's CI with the fix-formatting.yml workflow before version 26.43.0 and external pull requests can receive the format label.

Monkeytype repository CI workflow .github/workflows/fix-formatting.yml, prior to 26.43.0

What to do

  1. Update the Monkeytype repository to version 26.43.0 or later
  2. Review recent pull requests that received the format label for suspicious changes to workflows, code, or repository settings
  3. Rotate any tokens or secrets the CI workflow could access if the workflow ran untrusted code

Timeline

  1. 29 Oct 2026, 17:18 UTC
    Publicly disclosed
  2. 29 Oct 2026, 17:18 UTC
    Reported by NVD · NVD
  3. 29 Oct 2026, 17:20 UTC
    Picked up by Zero Radar

Sources 1 report, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-118762
CVSS
9.3 / 10
Disclosed
29 Oct 2026, 17:18 UTC
On Zero Radar
29 Oct 2026, 17:20 UTC (2 min after disclosure)
Last change
29 Oct 2026, 17:20 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

Monkeytype CI workflow lets outside code steal repository write access · Zero Radar