Attack Chain

1. An authenticated subuser gains minimal access to a Pterodactyl server, such as the ability to connect to the server's console (requiring websocket.connect permission).
2. The subuser makes an API request to a legitimate low-privilege endpoint on the Pterodactyl Panel, such as /api/client/servers/[...]/websocket or a file download endpoint, to obtain a panel-signed JSON Web Token (JWT).
3. The Pterodactyl Panel issues a JWT containing claims like server_uuid, user_uuid, and unique_id, which are used for various operations across the Panel and Wings.
4. The subuser intercepts and extracts this JWT.
5. The subuser then crafts an HTTP POST request to the Pterodactyl Wings /upload/file endpoint, including the obtained JWT as a query parameter (?token=).
6. The subuser includes arbitrary file content within the POST request, intending to upload it to the server.
7. The Pterodactyl Wings component, due to improper JWT scoping validation, accepts the JWT as valid for file upload, despite the token initially being issued for a different, lower-privilege action.
8. Wings proceeds to write the arbitrary file content to the server's file system, achieving unauthorized file upload and privilege escalation for the subuser.

Impact

This vulnerability allows any authenticated subuser, regardless of their specific permissions on a server, to upload arbitrary files to that server. While the attacker must already have subuser access to the target server, this flaw significantly escalates their privileges beyond what is explicitly granted, potentially leading to unauthorized data modification, execution of malicious scripts, or further system compromise. The impact is confined to the specific server the subuser has access to; users without any subuser access cannot exploit this vulnerability. The inability to properly control file uploads can lead to data integrity issues, denial of service through disk exhaustion, or remote code execution if the uploaded files are executed by vulnerable services on the server.

Recommendation

• Patch CVE-2026-54593: Upgrade Pterodactyl Panel to version 1.12.3 or newer, and Pterodactyl Wings to version 1.12.2 or newer immediately to mitigate CVE-2026-54593.
• Deploy the Sigma rule: Implement the provided Sigma rule in your SIEM to detect suspicious file upload attempts on the Pterodactyl Wings /upload/file endpoint. Tune this rule by identifying and allowlisting legitimate uses of this endpoint.
• Enable webserver logging: Ensure detailed webserver access logs are enabled for your Pterodactyl Wings instance to capture HTTP requests, including method, URI, query parameters, and status codes, which are crucial for detecting this activity.