CVE-2026-55378 JS Recon: Command injection in PR Branch Checker workflow via untrusted pull request context values
Remote attackers can execute arbitrary commands on GitHub Actions runners via shell metacharacters in pull request branch or fork names.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55378?
CVE-2026-55378 is a critical command injection vulnerability in shriyanss js-recon, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
JS Recon is a JavaScript enumeration and SAST tool. From 1.2.1-beta.1 until 1.3.1-beta.2, the PR Branch Checker workflow in .github/workflows/pr_checker.yml places github.head_ref and github.event.pull_request.head.repo.full_name into BRANCH_NAME and SOURCE_REPO and interpolates those untrusted values into a shell gh pr comment command. A remote user who opens a pull request can use shell metacharacters in a branch or fork name to execute commands in the GitHub Actions runner with the workflow's GITHUB_TOKEN, which has pull-requests write permission. This issue is fixed in version 1.3.1-beta.2.
Weakness: CWE-78
Which versions are affected by CVE-2026-55378?
How do I fix CVE-2026-55378?
No fix has been published for CVE-2026-55378 yet. Limit exposure of the affected software until one is available.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-55378 being exploited?
There is no known exploitation of CVE-2026-55378 in the wild and no public exploit code.
Sources
Also known as GHSA-w9cj-mg3x-qjm4.