CVE-2021-31924

mediumpriority · track · 27EPSS 0.003 · 26 %ileEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.33% (26th) EPSS

CVSS 4.6 · medium

Is it mine?

8 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · nvd

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

6.8

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.6mediumAV:L/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 3.9 · impact 6.4

v3.16.8mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 0.9 · impact 5.9

v3.16.8mediumAV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.16.2mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-287USprimaryCWE-287US

affected products (8)

Products and version ranges known to be affected.

n/a n/a≤ n/aenisa_euvdEU
Yubico pam-u2f1.1.0 → 1.1.1fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 8fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 9fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 10fstec_bduRU
fedoraproject fedora= 34nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
fedoraproject fedora= 35nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
yubico pam-u2f< 1.1.1nvdUScpe:2.3:a:yubico:pam-u2f:*:*:*:*:*:*:*:*

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu nvd NVD CVE.org MITRE

published 2021-05-26modified 2026-06-17

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+7718 more

references (19)

External citations — patches, advisories, analysis.

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