Insufficient verification of data authenticity in Keycloak - CVE-2026-6856
Published: September 10, 2026
Vulnerability identifier: #VU148955
CSH Severity: Low
CVSS v4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-6856
CWE-ID: CWE-345
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass acceptable AAGUID policy.
The vulnerability exists due to improper attestation validation in WebAuthn registration when processing packed self-attestation while direct attestation is requested. A remote user can register an authenticator using packed self-attestation to bypass acceptable AAGUID policy.
The AAGUID is unverified when the authenticator does not provide an x5c certificate chain.
Affected software
Keycloak
How to mitigate CVE-2026-6856
Install security update from vendor's website.
Keycloak - update to 26.6.2