Open WebUI: Open WebUI before 0.9.5 contains a stored cross-site scripting vulnerability in the OAuth…
Open WebUI
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- Severity
- Critical, CVSS 9.0
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
- Record
- CVE-2026-56398
- Affects
- Open WebUI
- Known exploited
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Published
- Record first published by the source
- July 15, 2026
- Source last modified
- July 16, 2026
Description
Open WebUI before 0.9.5 contains a stored cross-site scripting vulnerability in the OAuth authentication flow where the picture claim URL MIME type is inferred from file extension rather than Content-Type header, allowing SVG files to bypass the profile image validator and be stored as data URIs. Authenticated users who visit the profile image endpoint receive attacker-controlled SVG content with inline disposition and no default security headers, enabling script execution in the same origin to steal authentication tokens and achieve account takeover.
Description quoted from the NVD record.
Who is affected
This flaw affects Open WebUI, a chat interface that people use in a web browser, in all versions before 0.9.5. The problem is in the part that brings in a user's profile picture when they sign in through another account service (single sign-on). An attacker can slip in a harmful image file that gets saved as a profile picture. When a signed-in user views that picture, hidden code can run in their browser, steal the digital pass that keeps them signed in, and let the attacker take over their account. This flaw is rated Critical.
What to do
- Find out who runs Open WebUI for your organization: the person who installed it, or the IT provider or vendor who manages it. That person should handle the steps below.
- If you run it yourselves, update Open WebUI to version
0.9.5or later, which fixes this flaw. - If an IT provider or vendor runs it for you, send them this advisory and ask when the update to
0.9.5will be done. - After the update, check that Open WebUI shows version
0.9.5or later.
Analysis written from the source record as of July 16, 2026 and reviewed before publishing.