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Vulnerability record · CVE-2026-55158 · published 15 September 2026

CVE-2026-55158: OS command injection vulnerability

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.

9.1 CVSS 3.1 Critical EPSS 0.80% · top 45.1% CWE-78 · OS command injection Received
9.1CVSS 3.1 base score
0.80%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
6References
17 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References

LinkTags
https://github.com/wktk/conflibot/commit/0107ac6a4575ea200d0b92287ea58f975be9505d
https://github.com/wktk/conflibot/commit/59e255c49c920fd6b67471ab9ef3bf194439a3f2
https://github.com/wktk/conflibot/pull/329
https://github.com/wktk/conflibot/releases/tag/v1.2.1
https://github.com/wktk/conflibot/releases/tag/v2.0.0
https://github.com/wktk/conflibot/security/advisories/GHSA-2qvg-qr73-mqxp

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Source: NIST National Vulnerability Database (record CVE-2026-55158), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.