CVE-2026-48985: CWE-476: NULL Pointer Dereference in mcdope pam_usb
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions 0.9.1 and below, pusb_is_loginctl_local() can cause a NULL dereference crash when parsing loginctl output. The function calls popen() and reads the result; if the Remote field is only a newline, fgets() succeeds but strtok_r(buf, "\n", &saveptr) returns NULL. A subsequent strcmp(is_remote, "no") then dereferences NULL, causing undefined behavior (typically SIGSEGV) and crashing the PAM module. This can crash the authenticating process (e.g., sudo, login) and, depending on PAM stack configuration, deny access for all users of the affected service. This issue has been fixed in version 0.9.2.
AI Analysis
Technical Summary
pam_usb, a hardware authentication module for Linux using removable media, has a NULL pointer dereference vulnerability in versions 0.9.1 and earlier. The vulnerability occurs in the pusb_is_loginctl_local() function when parsing loginctl output. If the Remote field contains only a newline, strtok_r returns NULL, leading to a NULL pointer dereference in a subsequent strcmp call. This causes undefined behavior, typically a segmentation fault, crashing the PAM module and potentially denying access to users of affected services. The vulnerability has been addressed and fixed in version 0.9.2.
Potential Impact
Successful exploitation causes the PAM module to crash due to a NULL pointer dereference, which can terminate the authenticating process (e.g., sudo, login). Depending on the PAM stack configuration, this may result in denial of service by preventing users from authenticating. There is no impact on confidentiality or integrity reported.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later, where this NULL pointer dereference vulnerability is fixed. Patch status is confirmed by the vendor stating the issue is resolved in version 0.9.2. No other mitigation steps are indicated.
CVE-2026-48985: CWE-476: NULL Pointer Dereference in mcdope pam_usb
Description
pam_usb provides hardware authentication for Linux using ordinary removable media. In versions 0.9.1 and below, pusb_is_loginctl_local() can cause a NULL dereference crash when parsing loginctl output. The function calls popen() and reads the result; if the Remote field is only a newline, fgets() succeeds but strtok_r(buf, "\n", &saveptr) returns NULL. A subsequent strcmp(is_remote, "no") then dereferences NULL, causing undefined behavior (typically SIGSEGV) and crashing the PAM module. This can crash the authenticating process (e.g., sudo, login) and, depending on PAM stack configuration, deny access for all users of the affected service. This issue has been fixed in version 0.9.2.
CVSS v3.1
Score 5.5medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
pam_usb, a hardware authentication module for Linux using removable media, has a NULL pointer dereference vulnerability in versions 0.9.1 and earlier. The vulnerability occurs in the pusb_is_loginctl_local() function when parsing loginctl output. If the Remote field contains only a newline, strtok_r returns NULL, leading to a NULL pointer dereference in a subsequent strcmp call. This causes undefined behavior, typically a segmentation fault, crashing the PAM module and potentially denying access to users of affected services. The vulnerability has been addressed and fixed in version 0.9.2.
Potential Impact
Successful exploitation causes the PAM module to crash due to a NULL pointer dereference, which can terminate the authenticating process (e.g., sudo, login). Depending on the PAM stack configuration, this may result in denial of service by preventing users from authenticating. There is no impact on confidentiality or integrity reported.
Mitigation Recommendations
Upgrade pam_usb to version 0.9.2 or later, where this NULL pointer dereference vulnerability is fixed. Patch status is confirmed by the vendor stating the issue is resolved in version 0.9.2. No other mitigation steps are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-26T23:26:07.975Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a343000f198dc38c1384721
Added to database: 6/18/2026, 5:50:56 PM
Last enriched: 6/18/2026, 6:05:09 PM
Last updated: 6/19/2026, 2:46:38 AM
Views: 10
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