CVE-2026-55158 Conflibot: Command injection via crafted pull request branch names under pull_request_target
Attackers can execute arbitrary commands and steal secrets by crafting pull request branch names with shell metacharacters in Conflibot.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55158?
CVE-2026-55158 is a critical command injection vulnerability in wktk conflibot, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-78
Which versions are affected by CVE-2026-55158?
1 open source package ship an affected version, including wktk/conflibot.
| Package | Affected | Fixed in |
|---|---|---|
wktk/conflibot GitHub Actions | All versions | 1.2.1 |
How do I fix CVE-2026-55158?
Upgrade wktk/conflibot to 1.2.1 or later.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-55158 being exploited?
There is no known exploitation of CVE-2026-55158 in the wild and no public exploit code.
Sources
Also known as GHSA-2qvg-qr73-mqxp.