Monkeytype: Arbitrary code execution in CI workflow (CVE-2026-118762)
Monkeytype versions prior to 26.43.0 contain a vulnerability in the .github/workflows/fix-formatting.yml CI workflow, which uses the pull_request_target trigger with repository write permissions. An external contributor whose pull request receives the format label can execute arbitrary code, read or exfiltrate the GITHUB_TOKEN, and modify repository content.
CVE search metadata
CVE search record: CVE-2026-118762. Severity: critical. CVSS: 9.3. KEV: no. Product: Monkeytype (< 26.43.0). Brief: Monkeytype: Arbitrary code execution in CI workflow (CVE-2026-118762). Brief link: https://feed.craftedsignal.io/briefs/2026-10-monkeytype-ci-rce/
Triage facts
Revision 1- Applicability
- Monkeytype (< 26.43.0)
- Evidence
- Unknown
- Severity
- Critical
- Sources
- 1 public source
- Freshness
- Revision 1Oct 29, 21:10 UTC
- Vulnerabilities
- 1 CVE
- Source quality
- A2Roughly even chance
The Monkeytype repository CI workflow, specifically .github/workflows/fix-formatting.yml, is vulnerable to arbitrary code execution. Prior to version 26.43.0, the workflow runs on pull_request_target with write permissions and installs dependencies from fork-controlled files. Because actions/checkout persists the GITHUB_TOKEN while untrusted code executes, attackers can exfiltrate the token or perform unauthorized repository actions. This issue affects the CI pipeline, not the Monkeytype application or user data.