CVE-2026-45156 PUBLISHED

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

Assigner: GitHub_M
Reserved: 08.05.2026 Published: 01.06.2026 Updated: 01.06.2026

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.

Metrics

CVSS 3.1

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

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	Required	Availability Impact	None

CVSS 3.1

Product Status

Vendor	nextcloud
Product	security-advisories
Versions	Version >= 0.3.0, < 3.1.0 is affected Version >= 5.0.0, < 5.1.0 is affected Version >= 6.0.0, < 6.4.0 is affected

References

Problem Types

CWE-287: Improper Authentication CWE