Open WebUI has stored XSS via attacker-controlled file extension in /api/v1/audio/transcriptions

Exploitation

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

CVSS

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

EPSS

• CVE-2026-45315: 0.19% estimated exploitation activity in the next 30 days; percentile 8.31 (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 The audio transcription upload endpoint takes the file extension from the user-supplied filename and saves the file under CACHEDIR/audio/transcriptions/<uuid.<ext. The /cache/{path} route serves these files via FileResponse, which sets Content-Type from the on-disk extension and emits no Content-Disposition. A verified user with the default-on chat.stt permission can upload a polyglot WAV+HTML file named pwn.html and trick any other user into opening the resulting URL — the response comes back as text/html and any embedded <script runs in the Open WebUI origin. Details Verified on main @ 8dae237a (v0.9.2): - backend/openwebui/routers/audio.py:1244-1249 — ext = safename.rsplit('.', 1)[-1] from user-supplied filename, then filename = f'{id}.{ext}'. No allowlist, no cross-check against file.contenttype. - backend/openwebui/main.py:2768-2779 — /cache/{path:path} returns FileResponse(filepath). Starlette derives Content-Type from the filename extension and sets no…

Published by the source

14 May 2026, 20:17 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m8f9-9whg-f4xr

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m8f9-9whg-f4xr

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# Patch Next advisory brief: CVE-2026-45315

Advisory: Open WebUI has stored XSS via attacker-controlled file extension in /api/v1/audio/transcriptions
IDs: CVE-2026-45315, GHSA-m8f9-9whg-f4xr
Record: https://patchnext.com/advisories/cve-2026-45315 (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 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: open-webui 0.9.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI open-webui: affected <= 0.9.2; fixed in 0.9.3

## 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-m8f9-9whg-f4xr (OSV record GHSA-m8f9-9whg-f4xr lists affected ranges: PyPI open-webui >=0 <0.9.3 (fixed))
- Verified: https://github.com/advisories/GHSA-m8f9-9whg-f4xr (GitHub-reviewed advisory GHSA-m8f9-9whg-f4xr lists affected ranges: PyPI open-webui >=0 <=0.9.2)

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