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GHSA-8r6w-3qq5-4p4r
No affected components available
Summary
A privilege escalation vulnerability exists in the Wings /upload/file endpoint due to insufficient validation of panel-signed JWTs. Wings accepts any valid panel-signed JWT containing server_uuid, user_uuid, and unique_id, regardless of the token’s intended purpose. Because the Panel issues JWTs with these same claims for other lower-privilege operations (such as WebSocket authentication and file download links), an authenticated subuser can reuse one of those tokens to upload arbitrary files without possessing the required file.create permission.
Impact
Any subuser with permission to connect to a server's console, download files, or download backups could reuse those tokens to upload arbitrary files to the same server. A user that does not have access to a server as a subuser is not able to arbitrarily upload files.
Details
The panel generated JWT tokens for various purposes:
- https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Services/Backups/DownloadLinkService.php#L33-L36
- https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/FileUploadController.php#L45
- https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/WebsocketController.php#L58-L61
- https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/FileController.php#L82-L85
Though as the actual purpose is not conveyed part of the JWT tokens, this introduces this vulnerability of being able to do non-intended actions due to the expected fields (i.e.
server_uuid) on most endpoints being the same when parsing it on wings' side.
PoC
Create a new subuser that has the minimal amount of permissions on a server (websocket.connect). As that subuser, retrieve a websocket JWT token from the GET /api/client/servers/[...]/websocket endpoint (in my case, I manually just make a request under that user's browser session; you can probably just resend the /websocket request in browser console to get a fresh unused token). Using that websocket token, we can abuse this by directly using it in the /upload/file endpoint of the wings node instead of using it for websocket authentication:
import requests
wings_url = 'http://[...]:8080'
websocket_token = '[...]'
res = requests.post(f'{wings_url}/upload/file', params = {
'token': websocket_token,
}, files = {
'files': ('file-upload.txt', b'Hello, World!'),
})
print(res.status_code, res.content)
Observe, that even though our subuser never has permissions outside viewing the console, they are able to write arbitrary files in the server. This pattern happens in a lot of other action, but this is probably the most interesting one.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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