CVE-2021-40449: Microsoft Windows Win32k Privilege Escalation Vulnerability

Vulnerability summary

CVE-2021-40449 is a high (CVSS 7.8) Use After Free vulnerability in Microsoft Windows. It is known to be exploited: CISA lists it, first on 17-11-2021. It has been used in ransomware campaigns. EPSS estimates a 81.94% chance of exploitation in the next 30 days, higher than 99.6% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 13-10-2021
   PublishedVulnerability first disclosed.
2. 17-11-2021
   Added to CISA KEVMicrosoft Windows Win32k Privilege Escalation Vulnerability
3. 01-12-2021
   CISA remediation dueApply updates per vendor instructions.
4. 21-10-2025
   Last modifiedVulnerability information updated.

Description

Win32k Elevation of Privilege Vulnerability

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.