Medium severity · published Dec 5, 2025
CVE-2025-66558
Nextcloud Twofactor WebAuthn is the WebAuthn Two-Factor Provider for Nextcloud
4.3
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TW
Two-factor Webauthn · Nextcloud
1.0.0 before 1.4.2; 2.0.0 before 2.4.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66558
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66558
Patch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fr8x-mvjg-wf9q
Patch
https://github.com/nextcloud/twofactor_webauthn/commit/5d2302166d31ee2e01b2e21556bd5372156da13d
Issue Tracking
https://github.com/nextcloud/twofactor_webauthn/pull/881
Permissions Required
https://hackerone.com/reports/3360354