CVE-2026-48986: pam_usb: Infinite loop DoS in process-tree walk when parent process exits during authentication

Vulnerability summary

CVE-2026-48986 is a medium (CVSS 4.7) Infinite Loop vulnerability in mcdope pam_usb. EPSS estimates a 0.14% chance of exploitation in the next 30 days, higher than 3% of scored vulnerabilities.

Timeline

1. 18-06-2026
   PublishedVulnerability first disclosed.
2. 22-06-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.