CVE-2025-66558

Nextcloud Twofactor WebAuthn app was updated based on public key

MEDIUM
4.3
CVSS Score
Published: December 5, 2025 at 06:00 PM UTC
Updated: October 15, 2026 at 09:10 PM UTC
2 products affected across 1 vendorTwo Factor Webauthnsecurity-advisories

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Severity
MEDIUM4.3
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

All versions1.0.0 ≤ v < 1.4.22.0.0 ≤ v < 2.4.1

References (4)

x_refsource_MISCIssue TrackingPatch
Source: cverecord
https://github.com/nextcloud/twofactor_webauthn/pull/881
x_refsource_MISCPermissions RequiredVendor Advisory
Source: cverecord
https://hackerone.com/reports/3360354

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-639

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