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TI-2026-36238 Aliases CVE-2026-48982

pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race

Priority LOW 25CWE-362Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
Low · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, when updating a one-time pad file, a temporary file is created using open() without the O_EXCL flag. Without O_EXCL, the create operation is not atomic: two concurrent processes racing to update the same pad may both succeed in opening the file, with the second write silently overwriting the first. The one-time pad is the core replay-prevention mechanism of pam_usb. A successful race could result in the stored pad value diverging from what either process expected, potentially causing authentication failures or, in a precisely timed attack, creating a window for pad reuse. This issue has been fixed in version 0.9.2.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00118 1st percentileScored 2026-11-07
Fix Fixed pam_usb (mcdope): 0.9.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
mcdopepam_usbbefore 0.9.20.9.2Patch availableCNA
  • pam_usb Vendormcdope Affected before 0.9.2 Fixed in 0.9.2 Patch available CNA

Remediation

  • Fix · CNA pam_usb (mcdope) Fixed in 0.9.2

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48982

References

Other 2

  • TI-2026-35505 pam_usb: PAM_RHOST check skipped when deny_remote=false allows XDMCP authentication bypass CVSS 3.1HIGH 8.1
  • TI-2026-32598 pam_usb: Symlink attacks on pad directory and pad files enable authentication bypass and root file corruption CVSS 3.1HIGH 7.9
  • TI-2026-32596 pam_usb: PINENTRY_FALLBACK_APP environment variable allows arbitrary command execution CVSS 3.1HIGH 7.8
  • TI-2026-32600 pam_usb: Command injection via $TMUX environment variable leads to RCE as root CVSS 3.1HIGH 8.8
  • TI-2026-32599 pam_usb: Shell injection via device UUID and username in pamusb-conf and pamusb-agent CVSS 3.1HIGH 8.2
  • TI-2026-34849 pam_usb: deny_remote feature incorrectly classifies IPv4-mapped IPv6 remote connections as local CVSS 3.1HIGH 7.4
See all 21 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences