CVE-2026-48982
pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race
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Description
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, when updating a one-time pad file, a temporary file is created using open() without the O_EXCL flag. Without O_EXCL, the create operation is not atomic: two concurrent processes racing to update the same pad may both succeed in opening the file, with the second write silently overwriting the first. The one-time pad is the core replay-prevention mechanism of pam_usb. A successful race could result in the stored pad value diverging from what either process expected, potentially causing authentication failures or, in a precisely timed attack, creating a window for pad reuse. This issue has been fixed in version 0.9.2.
Remediation
No guide yetNo remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.
References (2)
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CVSS
- Attack Vector
- LOCAL
- Complexity
- HIGH
- Privileges
- LOW
- User Interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality
- LOW
- Integrity
- HIGH
- Availability
- LOW
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