CVE-2025-66558 Nextcloud Twofactor WebAuthn app was updated based on public key
An attacker can remove a victim's WebAuthn 2FA device by guessing a random string, forcing re-registration, due to missing ownership checks.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-66558?
CVE-2025-66558 is a low-severity missing authorization vulnerability in nextcloud security-advisories, published on 5 Dec 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-639
Which versions are affected by CVE-2025-66558?
It affects 1 product.
Products include Nextcloud Two-Factor Webauthn.
How do I fix CVE-2025-66558?
No fix has been published for CVE-2025-66558 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2025-66558 being exploited?
There is no known exploitation of CVE-2025-66558 in the wild and no public exploit code.
Sources
Also known as GHSA-fr8x-mvjg-wf9q.