Attack Chain

1. The attacker sends a GET request to /api/companies to obtain a company ID.
2. The attacker sends a GET request to /api/companies/{company_id}/execution-workspaces to enumerate execution workspaces and retrieve a workspace ID.
3. If the workspace is not in an active state, the attacker sends a PATCH request to /api/execution-workspaces/{workspace_id} with the body {"status": "active"} to reactivate it.
4. The attacker crafts a PATCH request to /api/execution-workspaces/{workspace_id} with a JSON body containing a malicious cleanupCommand within the config object, such as {"config": {"cleanupCommand": "echo RCE_PROOF > \\"/tmp/rce-proof.txt\\""}}.
5. The server stores the injected cleanupCommand in the workspace configuration.
6. The attacker triggers the command injection by sending a PATCH request to /api/execution-workspaces/{workspace_id} to archive the workspace, setting "status": "archived".
7. The server executes the injected command using child_process.spawn(shell, ["-c", cleanupCommand]).
8. The attacker achieves remote code execution on the server, potentially leading to data exfiltration, lateral movement, or other malicious activities.

Impact

Successful exploitation of this vulnerability allows an attacker to execute arbitrary commands on the Paperclip server with the privileges of the server process. This can lead to a range of severe impacts, including remote code execution, data exfiltration of sensitive information (e.g., system info, environment variables, source code), lateral movement within the network, and potential supply chain attacks by injecting backdoors into managed repositories. In local_trusted mode, this requires zero authentication, making it easily exploitable by malicious local processes or web pages.

Recommendation

• Apply input validation to the cleanupCommand and teardownCommand fields in the PATCH handler to prevent the injection of malicious commands.
• Implement command allowlisting, permitting only a predefined set of safe commands for workspace cleanup.
• Replace spawn(shell, ["-c", command]) with execFile() using an argument array to mitigate shell metacharacter injection.
• Implement proper authorization checks BEFORE processing the PATCH request to validate user permissions.
• Deploy the Sigma rule DetectPaperclipCleanupCommandInjection to identify attempts to exploit this vulnerability via the PATCH request to /api/execution-workspaces/:id.
• Run cleanup commands in a sandboxed environment to minimize the impact of potential exploits.