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TI-2026-35505 Aliases CVE-2026-48064

pam_usb: PAM_RHOST check skipped when deny_remote=false allows XDMCP authentication bypass

Priority HIGH 70CWE-863Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-863.

Summary

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.1, when a PAM service is configured with deny_remote=false in pam_usb (commonly done for display managers such as gdm-password or lightdm to bypass process/TTY heuristics for local sessions), the PAM_RHOST check in pusb_do_auth() is also skipped. PAM_RHOST is set by remote daemons (sshd, XDMCP servers) to identify the remote client address. Because the check is gated inside if (opts.deny_remote), a genuine remote XDMCP connection reaches the USB device authentication step instead of being rejected. This vulnerability is fixed in 0.9.1.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00342 27th percentileScored 2026-11-07
Fix Fixed pam_usb (mcdope): 0.9.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

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 0.9.10.9.1Patch availableCNA
  • pam_usb Vendormcdope Affected before 0.9.1 Fixed in 0.9.1 Patch available CNA

Remediation

  • Fix · CNA pam_usb (mcdope) Fixed in 0.9.1

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48064

References

Other 2

  • 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
  • TI-2026-34852 pam_usb: OTP pad authentication bypass via missing system pad check and uninitialized RNG buffer CVSS 3.1HIGH 7.1
See all 21 →

Sources

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