Arch Linux Security Advisory ASA-202106-16 ========================================== Severity: Medium Date : 2021-06-01 CVE-ID : CVE-2021-31924 Package : pam-u2f Type : authentication bypass Remote : No Link : https://security.archlinux.org/AVG-2001 Summary ======= The package pam-u2f before version 1.1.1-1 is vulnerable to authentication bypass. Resolution ========== Upgrade to 1.1.1-1. # pacman -Syu "pam-u2f>=1.1.1-1" The problem has been fixed upstream in version 1.1.1. Workaround ========== None. Description =========== Yubico pam-u2f before 1.1.1 has a logic issue that, depending on the pam-u2f configuration and the application used, could lead to a local PIN bypass. This issue does not allow user presence (touch) or cryptographic signature verification to be bypassed, so an attacker would still need to physically possess and interact with the YubiKey or another enrolled authenticator. If pam-u2f is configured to require PIN authentication, and the application using pam-u2f allows the user to submit NULL as the PIN, pam-u2f will attempt to perform a FIDO2 authentication without PIN. If this authentication is successful, the PIN requirement is bypassed. Impact ====== A local attacker could authenticate with a U2F device without having to enter the correct PIN. References ========== https://www.yubico.com/support/security-advisories/ysa-2021-03/ https://github.com/Yubico/pam-u2f/issues/175 https://github.com/Yubico/pam-u2f/pull/180 https://github.com/Yubico/pam-u2f/commit/6059b057dd9b6d0164fc16f9422c0d728f9... https://github.com/Yubico/pam-u2f/commit/1ffd435c9c26e8c3122ea121d3e0b55cb81... https://security.archlinux.org/CVE-2021-31924