Vulnerability · Published Jun 18, 2026 · Assigned by GitHub_M

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

Medium 5.8

In plain English

A medium-severity race condition in pam_usb from mcdope. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities).

Severity (CVSS 3.1)5.8Medium

Exploit odds (30 days)0.1%top 98.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
mcdope	pam_usb	< 0.9.2

Weakness: CWE-362 · Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L

References

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