CVE-2026-45156

Nextcloud: Authentication Bypass in ID4me handling via Missing JWT Signature Verification in User OIDC

State: Published
Severity: 8.1 High
Published: Jun 1, 2026
Updated: Jun 3, 2026
Reserved: May 8, 2026

Description

Nextcloud is an open source content collaboration platform. From versions 0.3.0 to before 3.1.0, 5.0.0 to before 5.1.0, and 6.0.0 to before 6.4.0, a missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user. This issue has been patched in versions 3.1.0, 4.1.0, 5.1.0, 6.4.0 and 8.3.0.

Scores

CVSS	Score	Vector	Source
3.1	8.1 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N	GitHub_M

Weaknesses

CWE-287 Improper Authentication

Affected Products

Product	Versions
security-advisoriesnextcloud	>= 0.3.0, < 3.1.0Affected >= 5.0.0, < 5.1.0Affected >= 6.0.0, < 6.4.0Affected

References

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