CVE-2026-28788
HIGHEPSS 85th pctlDescription
Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to version 0.8.6, any authenticated user can overwrite any file's content by ID through the `POST /api/v1/retrieval/process/files/batch` endpoint. The endpoint performs no ownership check, so a regular user with read access to a shared knowledge base can obtain file UUIDs via `GET /api/v1/knowledge/{id}/files` and then overwrite those files, escalating from read to write. The overwritten content is served to the LLM via RAG, meaning the attacker controls what the model tells other users. Version 0.8.6 patches the issue.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
Exploit Intelligence
Elevated risk: more likely to be exploited than 85% of all known CVEs.
References
Related Vulnerabilities
Other CWE-639 (Authorization Bypass Through User-Controlled Key) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-6875 | Critical | 9.8 | 90% | - | - |
| CVE-2024-46982 | High | 7.5 | 59% | - | Fix |
| CVE-2021-45428 | Critical | 9.8 | 57% | - | - |
| CVE-2019-17382 | Critical | 9.1 | 54% | - | Fix |
| CVE-2019-13360 | Critical | 9.8 | 24% | - | - |
| CVE-2023-48783 | Medium | 5.4 | 22% | - | Fix |
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-01.