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CVE-2026-48982

pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race

5.8 Medium

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.

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
Low
Integrity
High
Availability
Low

Exploit likelihood

0.12%Up 0.1 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.8

pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race

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.

Record
CVE-2026-48982
CVSS 3.1
5.8 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L
Weakness
CWE-362
Updated
2026-11-02
EUVDEUVD-2026-37935 5.8

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.

Record
EUVD-2026-37935
CVSS 3.1
5.8 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L
Updated
2026-11-02
NVD 5.8

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.

Record
CVE-2026-48982
CVSS 3.1
5.8 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L
Weakness
CWE-362
Updated
2026-11-02
OSV 5.8

pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race

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.

Record
CVE-2026-48982
CVSS 3.1
5.8 MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:L
Weakness
CWE-362
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-2026-48982 is a medium vulnerability (CVSS 5.8) 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 0.12%, the 1st percentile. No source names a fixed version.

References

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