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CVE-2026-48986

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

4.7 Medium

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.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.14%Up 0.1 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 4.7

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

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.

Record
CVE-2026-48986
CVSS 3.1
4.7 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-835
Updated
2026-11-02
EUVDEUVD-2026-37923 4.7

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.

Record
EUVD-2026-37923
CVSS 3.1
4.7 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
NVD 4.7

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.

Record
CVE-2026-48986
CVSS 3.1
4.7 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-835
Updated
2026-11-02
OSV 4.7

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

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.

Record
CVE-2026-48986
CVSS 3.1
4.7 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-835
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-48986 is a medium vulnerability (CVSS 4.7) in Mcdope Pam Usb, published June 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. No source names a fixed version.

References

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