Observable Response Discrepancy in Webauthn Framework - CVE-2024-39912
Published: July 14, 2024 / Updated: April 28, 2026
Vulnerability identifier: #VU128265
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2024-39912
CWE-ID: CWE-204
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Web-Authentication
Affected software:
Webauthn Framework
Webauthn Framework
Detailed vulnerability description
The vulnerability allows a remote attacker to enumerate valid usernames.
The vulnerability exists due to observable response discrepancy in ProfileBasedRequestOptionsBuilder when handling assertion options requests with a supplied username. A remote attacker can send a specially crafted request to enumerate valid usernames.
The issue is exposed when WebAuthn is used as the first or only authentication method.
How to mitigate CVE-2024-39912
Install security update from vendor's website.