Read the docs
TI-2026-36242 Aliases CVE-2026-48986

pam_usb: Infinite loop DoS in process-tree walk when parent process exits during authentication

Priority LOW 21CWE-835Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-835.

Summary

pam_usb provides hardware authentication for Linux using removable media. In pam_usb 0.9.1 and earlier, usb_get_process_parent_id() can cause an infinite loop DoS because it does not initialize *ppid on failure. In pusb_local_login(), the same variable is reused as input and output in a process-tree while loop; if /proc/<pid>/stat cannot be read (for example, when an ancestor process exits during authentication), the PID is not updated and the loop does not terminate. This hangs the authenticating process (such as sudo, sshd, or login) until it is forcibly terminated. This issue has been fixed in version 0.9.2.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00141 3rd 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-2026-48986

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