Critical RCE Bug Found in Homebrew Package Manager for macOS and Linux

A recently identified security vulnerability in the official Homebrew Cask repository could have been exploited by an attacker to execute arbitrary code on users’ machines that have Homebrew installed.

The issue, which was reported to the maintainers on April 18 by a Japanese security researcher named RyotaK, stemmed from the way code changes in its GitHub repository were handled, resulting in a scenario where a malicious pull request — i.e., the proposed changes — could be automatically reviewed and approved. The flaw was fixed on April 19.

Homebrew is a free and open-source software package manager solution that allows the installation of software on Apple’s macOS operating system as well as Linux. Homebrew Cask extends the functionality to include command-line workflows for GUI-based macOS applications, fonts, plugins, and other non-open source software.

“The discovered vulnerability would allow an attacker to inject arbitrary code into a cask and have it be merged automatically,” Homebrew’s Markus Reiter said. “This is due to a flaw in the git_diff dependency of the review-cask-pr GitHub Action, which is used to parse a pull request’s diff for inspection. Due to this…