Is CVE-2025-66558 in the CISA KEV catalog?

No. CVE-2025-66558 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-66558?

CVE-2025-66558 has a CVSS v3 base score of 3.1 (LOW).

What is the EPSS score for CVE-2025-66558?

CVE-2025-66558 has an EPSS score of 0.24% (14th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-66558?

Upgrade two-factor webauthn to 2.4.1 or later.

CVE & CISA-KEV Catalog

CVE-2025-66558

LOW

3.1

CVSS v3

NVD

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.

CWE-639Authorization Bypass Through User-Controlled Key

How to fix

Remediation Available

two-factor webauthnNVD

Affected:>= 2.0.0, < 2.4.1Fixed in:2.4.1CVE-2025-66558derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

0.24%probability of exploitation in 30 days

14thpercentile

Low risk: more likely to be exploited than 14% of all known CVEs.

References

Patch3

Vendor Advisory1

hackerone.com

Related Vulnerabilities

Other CWE-639 (Authorization Bypass Through User-Controlled Key) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-6875	Critical	9.8	90%	-	-
CVE-2024-46982	High	7.5	61%	-	Fix
CVE-2021-45428	Critical	9.8	57%	-	-
CVE-2019-17382	Critical	9.1	54%	-	Fix
CVE-2019-13360	Critical	9.8	24%	-	-
CVE-2023-48783	Medium	5.4	22%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-09.