Microsoft Patches Critical Security Flaw in Windows Last Month After Active Exploits Detected

A critical vulnerability within the Windows Common Log File System (CLFS), which could potentially allow attackers to escalate their privileges on affected systems, has been patched. Identified as CVE-2022–37969 and rated with a severity score of 7.8, Microsoft rectified this flaw in its September 2022 Patch Tuesday updates. It was highlighted that the vulnerability was already being exploited before the patch was released.

According to Microsoft, the vulnerability requires the attacker to have existing access and the capability to execute code on the target system. Zscaler's ThreatLabz team has revealed that they detected an exploit in the wild for this zero-day vulnerability on September 2, 2022. The security flaw stems from an inadequate bounds check in the cbSymbolZone field within the Base Record Header of the base log file (BLF) in the CLFS.sys driver, as detailed in their analysis.

The Windows CLFS serves as a versatile logging service utilized by applications in both user-mode and kernel-mode for recording data, events, and optimizing log file access. This service supports various applications, including online transaction processing (OLTP), compliance auditing, network event logging, and threat analysis.

Root of the Vulnerability: Zscaler explains that the vulnerability originates from a specific metadata block, known as the base record, found within the base log file created by the CreateLogFile() function. An attacker exploiting CVE-2022–37969 with a maliciously crafted base log file can cause memory corruption. This not only could lead to a system crash (manifesting as a blue screen of death) but also potentially allow for privilege escalation.

In addition to their analysis, Zscaler has provided proof-of-concept (PoC) guidelines to demonstrate how the vulnerability can be triggered, underscoring the importance for Windows users to update their systems to the latest version to guard against such threats.

For further insights into conducting Vulnerability Assessments, CyberNX is available for contact.

Disclaimer: The perspectives and opinions presented in this article are solely those of the author and do not involve Talha Javaid Khan in any capacity, nor does Talha Javaid Khan bear any responsibility for the content herein.

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