A flaw in Open WebUI’s chat message deletion endpoint allowed an authenticated user to cause the server to enter a synchronous infinite loop. The defect existed between versions 0.10.0 and 0.11.1 when the deletion helper traversed child message identifiers without recording if a node had already been visited. Triggering the loop by deleting a message in a cyclic chat tree would stall all requests handled by the process until it crashed or was restarted, effectively denying service to all users.

The vulnerability affects the open-webui open-webui product, specifically the versions from 0.10.0 through 0.11.1 inclusive. The issue was resolved in release 0.11.1, so any installations on those vulnerable versions are at risk.

The flaw carries a CVSS score of 6.5, indicating a moderate severity. The EPSS score is unavailable, and the vulnerability is not listed in CISA’s KEV catalog. Exploitation requires an authenticated user with access to delete messages; thus the attack vector is an authenticated API call. Once triggered, the effect is a server hang that blocks all user activity until the process is killed.