Microsoft February 2021 Patch Tuesday fixes 56 bugs, including an actively exploited Windows zero
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CVE-2021-24092
—1CVSS 3.1
7.8 high
EPSS
<1%p44
Published
()
Modified
Description
Microsoft Defender Elevation of Privilege Vulnerability
- Vendors
- microsoft
- Products
- windows defender, endpoint protection, security essentials, system center endpoint protection
- Weakness
- CWE-269
- Vector
- CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
In the news2 stories
Microsoft Defender's Own Driver Can Be Weaponized to Delete Security Software at Boot
Check Point revealed BTR Reforged, a technique weaponizing Microsoft Defender's built-in BTR.sys driver to delete security software at boot without exploiting any vulnerability.
Check Point Research disclosed BTR Reforged, a technique that abuses BTR.sys, a legitimately signed Windows Defender boot-time remediation driver, to perform arbitrary kernel-level file and registry operations on Windows 7 through Windows 11 25H2 without exploiting a software flaw. The BTR_CLI proof-of-concept tool, presented at Black Hat USA 2026 and DEF CON 34, installs the driver via direct registry writes and executes deletions during the boot-time 'golden window' before Defender's user-mode services start, demonstrated by deleting the full Defender stack on a patched Windows 11 machine. Exploitation requires SeLoadDriverPrivilege; Microsoft confirmed it does not meet criteria for immediate servicing and no patch is planned. No evidence of real-world abuse was found, and related indicators of compromise via Sysmon events were published.
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