Open WebUI 0.6.42 through 0.11.3 is vulnerable to uncontrolled resource consumption. An authenticated user can send chat messages that include compressed remote image URLs. The application downloads the image data and decompresses it without limiting size, allowing the attacker to consume server memory until the system becomes overwhelmed and all users experience a denial of service. The weakness involves excessive resource usage without bounds (CWE‑400) and also the failure to enforce size limits on compressed payloads (CWE‑409).

Affected products are Open WebUI in versions 0.6.42 up to but not including 0.11.4, including vendor open-webui. The vulnerability applies to any deployment where authenticated users have the ability to post compressed remote image URLs in chat or message content.

The CVSS base score is 7.1, indicating a high severity. EPSS is <1%, so the exploitation probability remains low but not zero. The vulnerability is not listed in CISA’s KEV catalog. The flaw is characterized by the resource exhaustion weaknesses CWE‑400 and CWE‑409 and requires an authenticated user who can supply a remote image URL that returns gzip‑encoded data. Once the image is fetched and decompressed, the server’s memory is exhausted, denying service to all users. The attack surface is limited to legitimate accounts that can send chat messages, but the denial of service impact is systemic.