The issue is a regular expression denial of service, where an attacker can supply a regex that forces catastrophic backtracking on the grep_knowledge_files function. When executed, the regex causes the event loop to block for approximately two seconds on each invocation. The weakness is listed as CWE-1333. Because the attacker must be authenticated, the impact is a denial of service for the particular user session and potentially a degradation of overall service quality when repeated calls are made.

Open WebUI versions 0.11.0 through 0.11.3 are affected. The vendor, open‑webui, released a fix in version 0.11.4.

The CVSS score of 5.3 indicates a moderate severity. EPSS score is less than 1% and the vulnerability is not listed in the CISA KEV catalog. Exploitation requires an authenticated session and the ability to trigger the grep_knowledge_files or grep_chat_files functions with a carefully crafted regex. Attackers can exploit this by instructing the model or by injecting the regex directly, resulting in repeated stalling that can degrade performance and potentially overwhelm a busy service.