{"id":"CVE-2026-55158","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-55158","generatedAt":"2026-09-20T15:04:15.783Z","title":"Prior to 1.2.1, src/index.ts builds git checkout, git merge, and git format-patch commands by interpolating the attacker-controlled pull request head.ref value into strings passed to exec.","description":"Conflibot warns in advance when merging a pull request will cause conflicts in other open pull requests. Prior to 1.2.1, src/index.ts builds git checkout, git merge, and git format-patch commands by interpolating the attacker-controlled pull request head.ref value into strings passed to exec. In the documented pull_request_target configuration, an attacker can open a pull request, including from a fork, whose branch name contains shell metacharacters, and the workflow automatically interprets those characters as commands without maintainer interaction. The commands execute on a runner with base-repository secrets and a write-scoped GITHUB_TOKEN, allowing arbitrary command execution, secret or token exfiltration, unauthorized pushes, and other token abuse. The fixed implementations in src/index.ts and src/conflibot.ts use execFile or spawn argument arrays, and the v2 line also uses numeric pull-request refs rather than branch names. This issue is fixed in versions 1.2.1 and 2.0.0.","published":"2026-09-15T15:17:19.000Z","lastModified":"2026-09-17T15:16:48.000Z","status":"Received","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"cwe":["CWE-78"],"affected":[],"epss":{"score":0.00445,"percentile":0.38069,"date":"2026-09-19","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.45%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/wktk/conflibot/commit/0107ac6a4575ea200d0b92287ea58f975be9505d","source":"security-advisories@github.com"},{"url":"https://github.com/wktk/conflibot/commit/59e255c49c920fd6b67471ab9ef3bf194439a3f2","source":"security-advisories@github.com"},{"url":"https://github.com/wktk/conflibot/pull/329","source":"security-advisories@github.com"},{"url":"https://github.com/wktk/conflibot/releases/tag/v1.2.1","source":"security-advisories@github.com"},{"url":"https://github.com/wktk/conflibot/releases/tag/v2.0.0","source":"security-advisories@github.com"},{"url":"https://github.com/wktk/conflibot/security/advisories/GHSA-2qvg-qr73-mqxp","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-55158","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}