The vulnerability arises when GitHub Copilot CLI discovers a malicious nested bare Git repository and unintentionally executes arbitrary shell commands specified in configuration keys such as core.fsmonitor. This flaw, classified under CWE‑696, enables an attacker to run any command during regular Git operations like status or diff, potentially leading to full code execution without user approval.

GitHub Copilot CLI versions before 1.0.43 are affected. Any installation of the CLI that allows a user or process to create or modify nested bare repositories inside a workspace is at risk.

With a CVSS score of 8.5, the vulnerability is considered high severity. Although the EPSS score is not available, the direct exploitation path—placing a bare repository with malicious config keys—is straightforward for users with write access to the repository’s directory. The flaw is not currently listed in the CISA KEV catalog, but its high impact and ease of exploitation suggest that it could be leveraged in both local and service contexts where the CLI runs with elevated privileges.