SB20260512122 - Multiple vulnerabilities in Microsoft Windows Common Log File System Driver

Description

This security bulletin contains information about 2 vulnerabilities.

1) Heap-based buffer overflow (CVE-ID: CVE-2026-40407)

CWE-ID: CWE-122 - Heap-based Buffer Overflow

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escalate privileges on the target system.

The vulnerability exists due to a boundary error in Windows Common Log File System Driver. A local user can pass specially crafted data to the application, trigger a heap-based buffer overflow and gain elevated priileges on the system.

2) Integer underflow (CVE-ID: CVE-2026-40397)

CWE-ID: CWE-191 - Integer underflow

CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear

The vulnerability allows a local user to escalate privileges on the target system.

The vulnerability exists due to integer underflow in Windows Common Log File System Driver. A local user can trigger integer underflow and gain elevated privileges on the system.

Remediation

Install update from vendor's website.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40407
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40397