Improper input validation in Open-Webui
CVE-2026-56398
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.006 (49.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 49.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Open-Webui — versions 0, 0.9.5
- Openwebui Open Webui
Weakness classification (CWE)
References
- github.com/open-webui/open-webui/security/advisories/GHSA-3wgj-c2hg-vm6q (Exploit, vendor-advisory, Vendor Advisory)
- www.vulncheck.com/advisories/open-webui-stored-cross-site-scripting-via-oauth-p… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-56398?
- CVE-2026-56398 is a high-severity vulnerability in Open-Webui, classified under Improper Input Validation. CVSS score: 7.3/10. Published 2026-07-15.
- How severe is CVE-2026-56398?
- High severity. CVSS v3 base score is 7.3 out of 10.