Open WebUI: master key generation flaw

Open WebUI

Open WebUI's Windows installer generates a master key from a linear congruential generator, allowing for blind recovery of the key.

Do this now

No source names a fix yet: limit who can reach Open WebUI until one does.

First seen: 6 Nov 2026
Last update: 6 Nov 2026, 05:17 UTC
Identifiers: CVE-2025-15603 ID not published yet
Source: news

Check this repository for exposure to one security incident from pwned.coffee. Report first, change nothing until I say so.

## Open WebUI: master key generation flaw
Severity: unknown. Patch status: fix status unknown.
Affected: Open WebUI
Ids: CVE-2025-15603

Open WebUI's Windows installer generates a master key from a linear congruential generator, allowing for blind recovery of the key.

## Steps
1. Search the repo, its CI and infra config for Open WebUI. If present, report the version in use and whether it's affected.
2. No source names a fix yet; check the vendor advisory. Until one ships: restrict network access to it.

## Report
A table: file, product or package, version in use, affected yes/no, exact fix. Then anything a human has to check outside the repo.

If you have the pwned.coffee MCP server (https://pwned.coffee/mcp), call lookup_cve("CVE-2025-15603") for the latest, and check_repo with this repo's lockfiles, Dockerfiles and workflows for a full receipt.
Sources: https://seclists.org/oss-sec/2026/q4/538
https://pwned.coffee/i/open-webui-master-key-generation-flaw-cve-2025-15603

Receipt

Exploitation: No known exploitation
Score: No CVSS published yet: severity unknown.
Last checked: 6 Nov 2026, 12:18 UTC

Sources: KEV – CVE record – Vendor –

Sources

seclists.org: Open WebUI: the Windows installer mints the master key from the install second — CVE-2025-15603 was rejected; here is the measurement

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