Auth bypass in Nextcloud Security-Advisories
CVE-2025-66558
Nextcloud Twofactor WebAuthn is the WebAuthn Two-Factor Provider for Nextcloud. Prior to 1.4.2 and 2.4.1, a missing ownership check allowed an attack to take-away a 2FA webauthn device when correctly guessing a 80-128 character long random string of letters, numbers and symbols. The victim would then be prompted to register a new device on the next login. The attacker can not authenticate as the victim. This vulnerability is fixed in 1.4.2 and 2.4.1.
Vulnerability class: IDOR (Insecure Direct Object Reference)
EPSS: 0.002 (15.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 3.1 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N.
Affected products
- Nextcloud Security-advisories — versions < 1.4.2, >= 2.0.0-beta.1, < 2.4.1
- Nextcloud Two-factor_webauthn
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Permissions Required, x_refsource_MISC, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66558?
- CVE-2025-66558 is a low-severity vulnerability in Nextcloud Security-Advisories, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 3.1/10. Published 2025-12-05.
- How severe is CVE-2025-66558?
- Low severity. CVSS v3 base score is 3.1 out of 10.