OctoPrint is Vulnerable to RCE Attacks via Unsanitized Filename in File Upload

Impact

OctoPrint versions up until and including 1.11.2 contain a vulnerability that allows an authenticated attacker to upload a file under a specially crafted filename that will allow arbitrary command execution if said filename becomes included in a command defined in a system event handler and said event gets triggered.

If no event handlers executing system commands with uploaded filenames as parameters have been configured, this vulnerability does not have an impact.

Patches

The vulnerability will be patched in version 1.11.3.

Workaround

Until the patch has been applied, OctoPrint administrators who have event handlers configured that include any kind of filename based placeholders (i.e. {__filename}, {__filepath}, {filename}, {path}, etc -- refer to the events documentation for a full list) should disable those by setting their enabled property to False or unchecking the "Enabled" checkbox in the GUI based Event Manager.

Alternatively, OctoPrint administrators should set feature.enforceReallyUniversalFilenames to true in config.yaml and restart OctoPrint, then vet the existing uploads and make sure to delete any suspicious looking files (e.g. those that contain a ; in their name followed by a command).

As always, OctoPrint administrators are advised to not expose OctoPrint on hostile networks like the public internet, and to vet who has access to their instance.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by @prabhatverma47.