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. 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 vulnerability has been patched in version 1.11.2.
Exploitability
AV:AAC:LPR:NUI:NScope
S:UImpact
C:NI:NA:H6.5/CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H