# 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.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-2qvg-qr73-mqxp

## 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 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-55158?

1 open source package ship an affected version, including wktk/conflibot.


| Package | Ecosystem | 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.

## Is CVE-2026-55158 being exploited?

There is no known exploitation of CVE-2026-55158 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55158 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-55158 in the wild and no public exploit code.

Affected packages and fixed versions:
- wktk/conflibot (GitHub Actions): affected all versions; fixed in 1.2.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55158/ (Markdown: https://insights.sbomify.com/CVE-2026-55158/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55158
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55158
- OSV: https://osv.dev/vulnerability/CVE-2026-55158

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55158/
Summaries are generated and may contain mistakes; the official description above is the record.