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CVE-2026-45156

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

Published: Jun 1, 2026Updated: Jun 1, 2026 Sources: CVE List NVD
NVD MITRE
8.1CVSS
HIGH

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.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available

CVSS Vector Breakdown

AV:NAC:LPR:NUI:RS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:RUser Interaction
Required
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None

Weaknesses

CWE-287

Affected Products

security-advisories
nextcloud

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qqgv-fqwp-mjpp
github.com
https://github.com/nextcloud/user_oidc/pull/1285
github.com
https://hackerone.com/reports/3489490
hackerone.com

Timeline

Published
Jun 1, 2026
Last Updated
Jun 1, 2026

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