CVE-2026-55158

CVE-2026-55158 is a critical-severity OS command injection vulnerability in wktk/conflibot (actions), affecting versions < 1.2.1. It is fixed in 1.2.1.

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Summary

conflibot vulnerable to command injection via crafted pull request branch names under pullrequesttarget

Affected configurations

Any workflow using wktk/conflibot at a version earlier than 1.2.1. The risk is highest under pull_request_target (the documented configuration), because that is where the write token and secrets are exposed to attacker-influenced refs.

Workarounds

There is no configuration-only workaround for affected versions. Upgrade to wktk/conflibot@v2. On GitHub-hosted runners this is a drop-in upgrade; self-hosted runners additionally need Node.js 24 support and git 2.38 or later.

Resources

Impact

Versions of conflibot before 1.2.1 build git commands by string interpolation and run them through a shell. Several of the interpolated values are pull request branch names (head.ref), which are attacker-controlled: anyone can open a pull request (including from a fork) whose head branch name contains shell metacharacters such as `, $( ), ;, |, or &.

The recommended workflow runs conflibot on the pull_request_target event, where the job has access to the base repository's secrets and a write-scoped GITHUB_TOKEN. As a result, a crafted branch name causes arbitrary command execution on the runner with that write token in the environment, allowing an attacker to exfiltrate secrets and the token, push to the repository, or otherwise abuse the token's permissions. No special privileges and no maintainer interaction are required, the action runs automatically when the pull request is opened.

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-55158 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.1); upgrading removes the vulnerable code path.

Affected versions

wktk/conflibot (< 1.2.1)

Security releases

wktk/conflibot → 1.2.1 (actions)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Fixed in 1.2.1 and 2.0.0. All git invocations now use argument arrays via execFile/spawn instead of a shell, so branch names can no longer be interpreted as shell syntax, and pull requests are referenced by number through refs/pull/<n>/head rather than by branch name.

Frequently Asked Questions

  1. What is CVE-2026-55158? CVE-2026-55158 is a critical-severity OS command injection vulnerability in wktk/conflibot (actions), affecting versions < 1.2.1. It is fixed in 1.2.1. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
  2. How severe is CVE-2026-55158? CVE-2026-55158 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
  3. Which versions of wktk/conflibot are affected by CVE-2026-55158? wktk/conflibot (actions) versions < 1.2.1 is affected.
  4. Is there a fix for CVE-2026-55158? Yes. CVE-2026-55158 is fixed in 1.2.1. Upgrade to this version or later.
  5. Is CVE-2026-55158 exploitable, and should I be worried? Whether CVE-2026-55158 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
  6. What actually determines whether CVE-2026-55158 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
  7. How do I fix CVE-2026-55158? Upgrade wktk/conflibot to 1.2.1 or later.

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