Authorization bypass through user-controlled key in Open WebUI - CVE-2026-28788
Published: April 24, 2026
Vulnerability identifier: #VU127475
CSH Severity: Low
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-28788
CWE-ID: CWE-639
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to overwrite arbitrary files and poison retrieval-augmented generation content.
The vulnerability exists due to improper access control in the process_files_batch() endpoint in backend/open_webui/routers/retrieval.py when handling crafted POST requests to /api/v1/retrieval/process/files/batch. A remote user can submit a file UUID and attacker-controlled content to overwrite arbitrary files and poison retrieval-augmented generation content.
Exploitation requires a valid account and knowledge of a target file UUID, which can be obtained from knowledge bases the user can read.
Affected software
Open WebUI
How to mitigate CVE-2026-28788
Install security update from vendor's website.
Open WebUI - update to 0.8.6