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-2026-55255 | High | 8.4 | 29% | KEV | Fix |
| CVE-2019-13360 | Critical | 9.8 | 24% | - | - |
Common questions
How do I fix CVE-2026-28788?
Upgrade open webui to 0.8.6 or later.
Is CVE-2026-28788 being actively exploited?
Not that we know of. CVE-2026-28788 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 2.9% is the estimated probability that it will be exploited in the next 30 days. That is higher than 85% of all scored CVEs.
How severe is CVE-2026-28788?
CVE-2026-28788 has a CVSS v3 base score of 7.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-28788 affect?
Published advisories record a fix for open webui (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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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.