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Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M

CVE-2026-55158Conflibot: Command injection via crafted pull request branch names under pull_request_target

Critical 9.1

In plain English

A critical-severity OS command injection in conflibot from wktk. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities).

Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.8%top 43.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
wktk conflibot < 1.2.1

Weakness: CWE-78 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References