CVE-2026-48983
pam_usb: TOCTOU race condition in pad directory creation allows symlink substitution
Description
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, a symlink race condition exists in per-device and per-user pad directory creation. pam_usb uses a check-then-act pattern: it calls lstat() to test for existence and then calls mkdir() separately to create the directory. A local attacker can win the race between these calls by replacing the target path with a symlink to a directory they control. If successful, one-time pad files may be written to an attacker-controlled location, potentially exposing future pad values before use or disrupting authentication. This issue has been fixed in version 0.9.2.
INFO
Published Date :
June 18, 2026, 8:16 p.m.
Last Modified :
Oct. 26, 2026, 11:10 a.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update pam_usb to version 0.9.2 or later.
- Remove any existing symlinks in pad directories.
- Verify pad files are created securely.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-48983.
| URL | Resource |
|---|---|
| https://github.com/mcdope/pam_usb/releases/tag/0.9.2 | |
| https://github.com/mcdope/pam_usb/security/advisories/GHSA-4j8q-67fq-3xc3 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-48983 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-48983
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-48983 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48983 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 26, 2026
Action Type Old Value New Value Added Translation Title: pam_usb de mcdope, Description: pam_usb proporciona autenticación de hardware para Linux utilizando medios extraíbles ordinarios. En versiones anteriores a la 0.9.2, existe una condición de carrera de enlace simbólico en la creación de directorios de pad por dispositivo y por usuario. pam_usb utiliza un patrón de verificar y luego actuar: llama a lstat() para comprobar la existencia y luego llama a mkdir() por separado para crear el directorio. Un atacante local puede ganar la carrera entre estas llamadas reemplazando la ruta de destino con un enlace simbólico a un directorio que controla. Si tiene éxito, los archivos de pad de un solo uso pueden escribirse en una ubicación controlada por el atacante, exponiendo potencialmente valores de pad futuros antes de su uso o interrumpiendo la autenticación. Este problema ha sido corregido en la versión 0.9.2. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 22, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-48983', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-22T12:41:19.864255Z'} -
New CVE Received by [email protected]
Jun. 18, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'mcdope', 'product': 'pam_usb', 'versions': [{'status': 'affected', 'version': '< 0.9.2'}]}] Added Description pam_usb provides hardware authentication for Linux using ordinary removable media. In versions prior to 0.9.2, a symlink race condition exists in per-device and per-user pad directory creation. pam_usb uses a check-then-act pattern: it calls lstat() to test for existence and then calls mkdir() separately to create the directory. A local attacker can win the race between these calls by replacing the target path with a symlink to a directory they control. If successful, one-time pad files may be written to an attacker-controlled location, potentially exposing future pad values before use or disrupting authentication. This issue has been fixed in version 0.9.2. Added CVSS V3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:L Added CWE CWE-367 Added Reference https://github.com/mcdope/pam_usb/releases/tag/0.9.2 Added Reference https://github.com/mcdope/pam_usb/security/advisories/GHSA-4j8q-67fq-3xc3