CVE-2025-66558

Name: CVE-2025-66558
Creator: NVD / NIST
Published: 2025-12-05T18:15:59.14+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.23%

Last modified Jun 17, 2026

CVE-2025-66558 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.23% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

0.23%

13.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-639

Affected Software

Vendor	Product	Versions
Nextcloud	Two-Factor Webauthn	>= 1.0.0, < 1.4.2
Nextcloud	Two-Factor Webauthn	>= 2.0.0, < 2.4.1

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-fr8x-mvjg-wf9qPatch, Vendor Advisory
https://github.com/nextcloud/twofactor_webauthn/commit/5d2302166d31ee2e01b2e21556bd5372156da13dPatch
https://github.com/nextcloud/twofactor_webauthn/pull/881Issue Tracking, Patch
https://hackerone.com/reports/3360354Permissions Required, Vendor Advisory

Timeline

Published: Dec 5, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-66558?

How severe is CVE-2025-66558?

CVE-2025-66558 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.23% probability of exploitation in the next 30 days.

How do I fix CVE-2025-66558?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-66558?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST