Monkeytype CI workflow: code execution with elevated token via fork pull request
Summary
The format-fixing GitHub Actions workflow of the Monkeytype repository runs on pull_request_target with write permissions and executes code from a fork pull request. An external contributor whose pull request receives the format label can run arbitrary code, read the GITHUB_TOKEN and push repository content or modify pull requests and issues. The typing test application and user data are not affected.
Affected
- Monkeytype repository versions before 26.43.0 (CI workflow .github/workflows/fix-formatting.yml)
- Forks of the repository that copied this workflow
Fixed in
- Fixed in Monkeytype 26.43.0 (fix commit 592ce1b)
Workaround
Unknown.
Exploitation
- No confirmed in-the-wild exploitation known.
- Third-party listings report no public proof of concept and no CISA KEV entry; the CVE was published on 2026-10-29, so this may change.
Our recommendation
- Update Monkeytype repositories and forks to 26.43.0 or include the fixed workflow.
- In your own repositories, do not run fork-controlled code under pull_request_target with write tokens.
- Require maintainer approval for workflow runs from external pull requests and set checkout to not persist credentials.
- Limit GITHUB_TOKEN permissions to the minimum needed.
- Check whether your own repositories use similar workflows.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Fix commit 592ce1b github.com
- Release v26.43.0 github.com
- GitHub Security Advisory GHSA-47v3-j88w-92f8 github.com
- VulnerableDB entry (NVD mirror) vulners.com
- VulDB entry vuldb.com
- Strix CVE overview www.strix.ai
- SecurityFocus CVE entry www.securityfocus.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 00:27.
Original description (NVD)
Monkeytype is a minimalistic and customizable typing test. Prior to 26.43.0, the .github/workflows/fix-formatting.yml workflow runs on pull_request_target with repository write permissions, checks out a fork pull request, installs dependencies from the fork's package.json, and invokes the fork-controlled oxfmt binary. Because actions/checkout persists the elevated GITHUB_TOKEN in Git configuration until after untrusted code executes, an external contributor whose pull request receives the format label can run arbitrary code, read or exfiltrate the token, and push repository content or modify pull requests and issues. The issue affects the repository CI workflow, not the Monkeytype application or user data. This issue is fixed in version 26.43.0.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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