Open WebUI vulnerable to stored XSS via OAuth picture claim stored as SVG data URI in profile_image_url

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-56398: 0.64% estimated exploitation activity in the next 30 days; percentile 50.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When a user signs in via OAuth, Open WebUI fetches the picture claim URL, infers a MIME type from the URL extension via mimetypes.guesstype, and stores data:<mime;base64,... as the user's profile image. The OAuth code path does not go through the validateprofileimageurl Pydantic validator that normally restricts profile images to PNG/JPEG/GIF/WebP. A .svg URL in the picture claim lands in the database as data:image/svg+xml;base64,.... The profile image endpoint GET /api/v1/users/{id}/profile/image returns the stored data URI with the attacker-controlled MIME type as Content-Type and Content-Disposition: inline. Security headers (CSP, X-Content-Type-Options) are env-gated and not set by default. An authenticated user navigating directly to that URL gets the SVG as a top-level document, executing <script/onload in the same origin and able to read localStorage.token → account takeover. Same class of trust-boundary error as CVE-2025-64496 (trust of untrusted model servers) and…

Published by the source

14 May 2026, 20:27 UTC

Last modified by the source

16 Jul 2026, 03:56 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3wgj-c2hg-vm6q

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3wgj-c2hg-vm6q

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# Patch Next advisory brief: CVE-2026-56398

Advisory: Open WebUI vulnerable to stored XSS via OAuth picture claim stored as SVG data URI in profile_image_url
IDs: CVE-2026-56398, GHSA-3wgj-c2hg-vm6q
Record: https://patchnext.com/advisories/cve-2026-56398 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: open-webui 0.9.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI open-webui: affected <= 0.9.4; fixed in 0.9.5

## Suggested inspection (read-only)
- `python -m pip show open-webui`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on open-webui.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3wgj-c2hg-vm6q (OSV record GHSA-3wgj-c2hg-vm6q lists affected ranges: PyPI open-webui >=0 <0.9.5 (fixed))
- Verified: https://github.com/advisories/GHSA-3wgj-c2hg-vm6q (GitHub-reviewed advisory GHSA-3wgj-c2hg-vm6q lists affected ranges: PyPI open-webui >=0 <=0.9.4)

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