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Vulnerability record · CVE-2026-45156 · published 1 June 2026

CVE-2026-45156: Improper authentication vulnerability

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.

8.1 CVSS 3.1 High EPSS 0.55% · top 56.0% CWE-287 · Improper authentication Deferred
8.1CVSS 3.1 base score
0.55%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
22 Jul 2026Last modified by NVD

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.

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

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-45156), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.