What is CVE-2026-45156?

CVE-2026-45156 is a high-severity vulnerability in Nextcloud Security-advisories, classified under Improper Authentication. CVSS score: 8.1/10. Published 2026-06-01.

How severe is CVE-2026-45156?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in Nextcloud Security-advisories

CVE-2026-45156

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 identif…

Vulnerability class: Broken Authentication

EPSS: 0.000 (8.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.

Affected products

Nextcloud Security-advisories — versions >= 0.3.0, < 3.1.0, >= 5.0.0, < 5.1.0, >= 6.0.0, < 6.4.0

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

security-advisories@github.com (x_refsource_CONFIRM)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-45156?: CVE-2026-45156 is a high-severity vulnerability in Nextcloud Security-advisories, classified under Improper Authentication. CVSS score: 8.1/10. Published 2026-06-01.
How severe is CVE-2026-45156?: High severity. CVSS v3 base score is 8.1 out of 10.