CVE-2021-31924 Auth bypass in n/a
Local attackers can bypass PIN authentication in Yubico pam-u2f if configured to require PIN and the application allows NULL input, though physical key possession is still required.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-31924?
CVE-2021-31924 is a medium-severity authentication bypass vulnerability in Fedoraproject Fedora, published on 25 May 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-287
Which versions are affected by CVE-2021-31924?
It affects 2 products.
Products include Fedoraproject Fedora, Yubico Pam-U2f.
How do I fix CVE-2021-31924?
Upgrade to a fixed version.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2021-31924 being exploited?
There is no known exploitation of CVE-2021-31924 in the wild and no public exploit code.
Other vulnerabilities in Fedoraproject Fedora
Sources
Also known as DEBIAN-CVE-2021-31924, GHSA-v2qj-ch59-r5g4.