CVE-2021-31924

NameCVE-2021-31924
DescriptionYubico 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
NVD severitymedium
Debian Bugs987545

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
pam-u2f (PTS)stretch1.0.4-2fixed
buster1.0.7-1+deb10u1fixed
bullseye, sid1.1.0-1.1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
pam-u2fsourcestretch(not affected)
pam-u2fsourcebuster(not affected)
pam-u2fsource(unstable)1.1.0-1.1987545

Notes

[buster] - pam-u2f <not-affected> (Vulnerable code not present)
[stretch] - pam-u2f <not-affected> (Vulnerable code not present)
https://www.yubico.com/support/security-advisories/ysa-2021-03
https://github.com/Yubico/pam-u2f/commit/6059b057dd9b6d0164fc16f9422c0d728f902bb5 (pam_u2f-1.1.1)
https://github.com/Yubico/pam-u2f/issues/175
Support for PIN verification introduced in 1.1.0.

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