CVE-2026-45284: Nextcloud: Wrong condition in the User OIDC app's LdapService allowed deleted LDAP users to authenticate

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-01 · updated 2026-07-22
Weakness: CWE-284

Description

Nextcloud is an open source content collaboration platform. From version 1.3.6 to before version 8.4.0, an improper check allowed users that where provided by LDAP to still authenticate towards user OIDC after they where deleted. This issue has been patched in version 8.4.0.

Affected products

nextcloud User Oidc: from 1.3.6 before 8.4.0 — fixed in 8.4.0

How to fix

Upgrade to a fixed version: nextcloud User Oidc 8.4.0. Check the vendor advisory for mitigations.

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-79xf-ffj8-96fm
https://github.com/nextcloud/user_oidc/pull/1340
https://hackerone.com/reports/3554696

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