What’s Vulnerable › Vulnerabilities

CVE-2026-48982: pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race

• Severity: medium (CVSS 5.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-18 · updated 2026-10-26
• Weakness: CWE-362

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.

Affected products

• mcdope pam_usb: before 0.9.2

References

• https://github.com/mcdope/pam_usb/releases/tag/0.9.2
• https://github.com/mcdope/pam_usb/security/advisories/GHSA-hxh6-9574-5vp6

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