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.

CVSS 3.1

4.3CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS

0.3% chance of exploitation in the next 30 days; higher than 20% of CVEs (scores of 2026-10-25)

CWE

CWE-639

Published

2025-12-05

Modified

2026-10-15

Record from

the NVD, synced 2026-10-19

Affected

• nextcloud:two-factor_webauthn

References

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fr8x-mvjg-wf9q
• https://github.com/nextcloud/twofactor_webauthn/commit/5d2302166d31ee2e01b2e21556bd5372156da13d
• https://github.com/nextcloud/twofactor_webauthn/pull/881
• https://hackerone.com/reports/3360354

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