Description
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.
CVSS breakdown
CVSS 3.1
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Affected products
- mcdope / pam_usb< 0.9.1 – < 0.9.1