CVE-2021-31924

MEDIUM
6.8
CVSS Score
Published: May 25, 2021 at 11:40 PM UTC
Updated: June 17, 2026 at 03:52 AM UTC
2 products affected across 2 vendorsFedoraPam U2F

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Severity
MEDIUM6.8
Exploit prediction
EPSS 0.3%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.1.1
Affected range stops below 1.1.1, so it looks safe — our inference, not a vendor statement

CVSS

Attack Vector
PHYSICAL
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-287

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