CISA Warns of Windows Privilege Escalation Vulnerability Exploited in Attacks
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CISA has issued an urgent security advisory, adding Microsoft Windows privilege escalation <\/a>vulnerability CVE-2021-43226 to its Known Exploited Vulnerabilities (KEV) catalog on October 6, 2025.\u00a0<\/p>\n The vulnerability affects the Microsoft Windows Common Log File <\/a>System <\/a>(CLFS)<\/a> Driver and poses significant security risks to enterprise environments.<\/p>\n The CVE-2021-43226 vulnerability resides within Microsoft\u2019s Common Log File System Driver, a core Windows component responsible for managing transaction logging operations.\u00a0<\/p>\n This privilege escalation flaw allows local, authenticated attackers with existing system access to bypass critical security mechanisms and elevate their privileges to SYSTEM level access.<\/p>\n According to Microsoft\u2019s Security Response Center, the vulnerability stems from improper validation of user-supplied data within the CLFS driver\u2019s memory management routines.\u00a0<\/p>\n Attackers can exploit this weakness by crafting malicious CLFS log files that trigger buffer overflow conditions, leading to arbitrary code execution with elevated privileges.\u00a0<\/p>\n The exploit requires local access and standard user privileges as prerequisites, making it particularly dangerous in enterprise environments where attackers have already gained an initial foothold through phishing or social engineering attacks<\/a>.<\/p>\n The vulnerability affects multiple Windows versions, including Windows 10, Windows 11<\/a>, Windows Server 2016, Windows Server 2019, and Windows Server 2022.\u00a0<\/p>\n Security researchers have identified proof-of-concept exploit code circulating in underground forums, increasing the likelihood of active exploitation campaigns.<\/p>\nMicrosoft Windows Privilege Escalation Flaw (CVE-2021-43226)<\/strong><\/h2>\n