When the Semaphore scheduler process triggers a git ls-remote operation to poll for commit changes, the malicious git_url is interpreted as a command-line option rather than a repository path. Consequently, the git binary executes the injected command via a shell. This operation occurs within the primary Semaphore server process, allowing the attacker to bypass remote runner isolation and gain full access to the server host, including master encryption keys and all stored project secrets.

Attack Chain

1. Attacker authenticates to the Semaphore instance with a standard Manager or Owner role.
2. Attacker creates an SSH key entry in the project to satisfy repository requirements.
3. Attacker sends a POST request to /api/project/{id}/repositories with a crafted git_url payload containing a malicious --upload-pack argument (e.g., --upload-pack=bash -c "COMMAND").
4. Attacker creates a new project template linked to the repository containing the malicious git_url.
5. Attacker creates a schedule for the project, which flags the repository for automatic polling.
6. The Semaphore server process polls the repository via the internal SchedulePool service, triggering the git ls-remote command.
7. The system git binary parses the injected option and executes the payload through the shell.
8. Attacker gains a reverse shell or executes arbitrary commands with the privileges of the Semaphore server process.

Impact

Successful exploitation results in full remote code execution on the server host. Attackers can gain access to the application's internal database, environment variables, master encryption keys (access_key_encryption), and all secrets configured across every project in the instance. This affects any deployment using the default cmd_git client configuration.

Recommendation

1. Upgrade Semaphore immediately to a version containing the patch for CVE-2026-73294 (v0.0.0-20260704181911-7e8a9434bd81 or later).
2. Audit user permissions within the platform to identify and revoke excessive Manager or Owner roles assigned to untrusted accounts.
3. Implement egress filtering on the Semaphore server host to prevent unexpected outbound connections (e.g., reverse shells) initiated by the application process.