CVE-2026-48986: CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') in mcdope pam_usb
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.
AI Analysis
Technical Summary
The vulnerability in pam_usb (CVE-2026-48986) involves an infinite loop caused by an uninitialized and reused variable (*ppid) in the function usb_get_process_parent_id(). When /proc/<pid>/stat cannot be read, such as when an ancestor process exits during authentication, the PID tracking variable is not updated, causing the while loop in pusb_local_login() to never exit. This results in a denial of service by hanging authentication processes like sudo, sshd, or login. The flaw affects pam_usb 0.9.1 and earlier and has been fixed in version 0.9.2.
Potential Impact
The vulnerability leads to a denial of service condition by causing authentication processes to hang indefinitely. This affects local authentication mechanisms relying on pam_usb, potentially blocking legitimate user access until the affected process is forcibly terminated. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later, where this infinite loop issue has been fixed. No other mitigations are indicated.
CVE-2026-48986: CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') in mcdope pam_usb
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.
CVSS v3.1
Score 4.7medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in pam_usb (CVE-2026-48986) involves an infinite loop caused by an uninitialized and reused variable (*ppid) in the function usb_get_process_parent_id(). When /proc/<pid>/stat cannot be read, such as when an ancestor process exits during authentication, the PID tracking variable is not updated, causing the while loop in pusb_local_login() to never exit. This results in a denial of service by hanging authentication processes like sudo, sshd, or login. The flaw affects pam_usb 0.9.1 and earlier and has been fixed in version 0.9.2.
Potential Impact
The vulnerability leads to a denial of service condition by causing authentication processes to hang indefinitely. This affects local authentication mechanisms relying on pam_usb, potentially blocking legitimate user access until the affected process is forcibly terminated. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later, where this infinite loop issue has been fixed. No other mitigations are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-26T23:26:07.975Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a343000f198dc38c1384725
Added to database: 6/18/2026, 5:50:56 PM
Last enriched: 6/18/2026, 6:05:04 PM
Last updated: 6/18/2026, 10:38:50 PM
Views: 5
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