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CVE Record

CVE-2011-4120: Yubico PAM Module before 2.10 performed user authentication when 'use_first_pass' PAM configuration option...

Yubico PAM Module before 2.10 performed user authentication when 'use_first_pass' PAM configuration option was not used and the module was configured as 'sufficient' in the PAM configuration. A remote attacker could use this flaw to circumvent common authentication process and obtain access to the account in question by providing a NULL value (pressing Ctrl-D keyboard sequence) as the password string.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

An old Yubico PAM module flaw could let a remote login bypass the normal password check when the PAM stack was configured in a specific weak way: module marked sufficient and not using use_first_pass. If that legacy setup still exists, an attacker could access the targeted account using a null password value.

Executive priority

Prioritize this for any legacy system using YubiKey-backed PAM authentication for remote access. It is not broadly internet-wide by default, but the business impact is high where the vulnerable configuration exists because it can undermine account login controls.

Technical view

CVE-2011-4120 affects yubico-pam before 2.10. In PAM configurations where the module is sufficient and use_first_pass is absent, authentication could proceed incorrectly when the password string was null, bypassing the common authentication path. The source bundle provides no CVSS, CWE, or KEV listing.

Likely exposure

Exposure is likely limited to legacy Linux/Unix systems using yubico-pam before 2.10 with the specific PAM option combination described. Systems not using yubico-pam, using newer packages, or enforcing use_first_pass are not shown as affected by the provided sources.

Exploitation context

The bundle describes remote account access through authentication bypass, but provides no evidence of active exploitation and kev is false. Exploitation depends on a vulnerable yubico-pam version and the risky PAM configuration being reachable through a remote authentication service.

Researcher notes

The public bundle is sparse: no CVSS vector, no CWE, and no KEV entry. The key technical preconditions are version before 2.10, yubico-pam configured as sufficient, and use_first_pass absent. Avoid assuming impact beyond accounts protected by that PAM path.

Mitigation direction

  • Inventory systems using yubico-pam and identify versions before 2.10.
  • Upgrade affected yubico-pam packages to 2.10 or later where available.
  • Review PAM service files for sufficient yubico-pam entries missing use_first_pass.
  • Check Debian, Red Hat, and Yubico guidance for distro-specific remediation.
  • Restrict remote access to affected authentication services until remediated.

Validation and detection

  • Confirm installed yubico-pam package versions on Linux/Unix hosts.
  • Review PAM configuration for the exact sufficient and missing use_first_pass condition.
  • Verify remote login paths that rely on the vulnerable PAM stack.
  • Check vendor package advisories for fixed builds on each distribution.
  • Document whether each host is affected, not affected, or requires manual review.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2011-4120 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
yubico-pamyubico-pambefore 2.10Listed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.