OctoPrint Vulnerable to Denial of Service through malformed HTTP request in OctoPrint

Overview

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows any unauthenticated attacker to send a manipulated broken multipart/form-data request to OctoPrint and through that make the web server component become unresponsive. This could be used to effectively run a denial of service attack on the OctoPrint server.

Patches

The vulnerability has been patched in version 1.11.2.

Workaround

OctoPrint administrators are once more reminded to not make OctoPrint available on hostile networks (e.g. the internet), regardless of whether this vulnerability is patched or not.

Details

The issue can be triggered by a broken multipart/form-data request lacking an end boundary to any of OctoPrint's endpoints implemented through the octoprint.server.util.tornado.UploadStorageFallbackHandler request handler. The request handler will get stuck in an endless busy loop, looking for a part of the request that will never come. As Tornado is single-threaded, that will effectively block the whole web server.

The fix adds detection of invalid requests like that and ensures they are handled gracefully with an HTTP 400 Bad Request response.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Affected packages

• octoprint < 1.11.2

Remediation

Upgrade to a patched release:

• octoprint 1.11.2