Microsoft · Windows Applocker · CVE-2024-21338
**Name of the Vulnerable Software and Affected Versions**
Windows 10 (affected versions not specified)
Windows 11 (affected versions not specified)
**Description**
An elevation of privilege issue exists in the Windows kernel, specifically within the AppLocker driver `appid.sys`. The flaw stems from an exposed IOCTL (Input/Output Control) with insufficient access control, which allows an attacker with Administrator privileges to cross the boundary into the kernel. By abusing an untrusted pointer exposed through a kernel IOCTL, an attacker can call a user-controlled function pointer in kernel mode. Specifically, the exploit can use `ExpProfileDelete()` as a target to decrement `PreviousMode` from 1 to 0, causing `NtWriteVirtualMemory()` and `NtReadVirtualMemory()` to bypass security checks. This enables the manipulation of process tokens to obtain full SYSTEM privileges, even on systems with HVCI (Hypervisor-Protected Code Integrity) enabled. This issue has been exploited in the wild as a zero-day by the Lazarus group and has been utilized by the Mallox ransomware family and the BlackCat/ALPHV group.
**Recommendations**
At the moment, there is no information about a newer version that contains a fix for this vulnerability.