CVE-2026-48982 pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race
A race condition in pam_usb allows concurrent updates to corrupt one-time pads, potentially enabling authentication bypass or failures.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-48982?
CVE-2026-48982 is a medium-severity vulnerability in mcdope pam_usb, published on 18 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Weakness: CWE-362
Which versions are affected by CVE-2026-48982?
How do I fix CVE-2026-48982?
No fix has been published for CVE-2026-48982 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-48982 being exploited?
There is no known exploitation of CVE-2026-48982 in the wild and no public exploit code.
Sources
Also known as GHSA-hxh6-9574-5vp6.