# Auth bypass flaws in YunoHost SOGo app

Published: 2026-09-30 · Severity: routine · Sectors: technology
Canonical: https://vorant.io/reports/c3109008-a727-5f32-9d17-202d99bb4863/auth-bypass-flaws-in-yunohost-sogo-app

> Two vulnerabilities in the YunoHost sogo_yhn package let unauthenticated attackers log in as any user, including admins, without a valid password.

CERT Polska coordinated disclosure of two authentication bypass vulnerabilities in the sogo_yhn YunoHost application package, which configures the SOGo groupware server. CVE-2026-74864 stems from sogo_yhn configuring SOGo to trust the 'x-webobjects-remote-user' HTTP header as proof of authentication; because Nginx does not strip this header, any client can set it arbitrarily and impersonate any user, including privileged accounts, with no password required. CVE-2026-74865 arises from the 'SOGoTrustProxyAuthentication=YES' setting, which causes HTTP Basic authentication to skip password verification entirely — an attacker who knows only a valid username can log in as that user with any password value.

Both issues represent complete authentication bypass on affected SOGo/YunoHost deployments, allowing full account takeover including administrative access, without requiring any prior credentials or user interaction. There is no indication in the report of in-the-wild exploitation; this is a coordinated, responsibly disclosed report credited to Przemysław Knycz (WeKrwi.IT).

The vulnerabilities were fixed in sogo_yhn version 5.8.0~ynh9. Defenders running YunoHost with the sogo_yhn app should upgrade immediately to this or a later version, and audit SOGo/Nginx proxy configurations to ensure the x-webobjects-remote-user header is stripped or not trusted from untrusted network paths, and that SOGoTrustProxyAuthentication is not enabled unless the environment strictly requires and secures proxy-based authentication.

## Mentioned in this report

- Vulnerabilities: CVE-2026-74864, CVE-2026-74865

Source reporting: https://cert.pl/en/posts/2026/09/CVE-2026-74864

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