How severe is CVE-2025-66558?

CVE-2025-66558 has a CVSS 3.x base score of 3.1, rated low severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2025-66558 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66558?

CVE-2025-66558 affects Nextcloud Two-factor Webauthn. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-66558?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-66558 have an EU (EUVD) identifier?

Yes. CVE-2025-66558 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201460.

When was CVE-2025-66558 published?

CVE-2025-66558 was published on 2025-12-05 and last updated on 2026-06-17.

CVE-2025-66558

CVE-2025-66558 is a low-severity vulnerability in Nextcloud Two-factor Webauthn with a CVSS 3.x base score of 3.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-639.

Key facts

Severity: Low (CVSS 3.x base score 3.1)
EPSS exploit prediction: 0% (14th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-201460
Weakness: CWE-639
Affected product: Nextcloud Two-factor Webauthn
Published: 2025-12-05
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-66558?: CVE-2025-66558 has a CVSS 3.x base score of 3.1, rated low severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2025-66558 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66558?: CVE-2025-66558 affects Nextcloud Two-factor Webauthn. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-66558?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66558 have an EU (EUVD) identifier?: Yes. CVE-2025-66558 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201460.
When was CVE-2025-66558 published?: CVE-2025-66558 was published on 2025-12-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nextcloud:two-factor_webauthn:*:*:*:*:*:*:*:*

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