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

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Summary

CVECVE-2026-45156
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-01 17:17:09 UTC
Updated2026-06-01 18:14:29 UTC
DescriptionNextcloud 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.

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from [email protected]

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

EPSS: 0.000280000 probability, percentile 0.085320000 (date 2026-06-04)

Problem Types: CWE-287 | CWE-287 CWE-287: Improper Authentication

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nextcloud Security-advisories affected >= 0.3.0, < 3.1.0 Not specified
CNA Nextcloud Security-advisories affected >= 5.0.0, < 5.1.0 Not specified
CNA Nextcloud Security-advisories affected >= 6.0.0, < 6.4.0 Not specified

References

ReferenceSourceLinkTags
github.com/nextcloud/security-advisories/security/advisories/GHSA-qqgv-f... [email protected] github.com
github.com/nextcloud/user_oidc/pull/1285 [email protected] github.com
hackerone.com/reports/3489490 [email protected] hackerone.com
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