CVE-2023-21264 - Insider Look into Hypervisor Memory Access, Exploitation and Solution

Yet another Common Vulnerabilities and Exposures (CVE) alert has surfaced, with the identifier CVE-2023-21264. At its core, the issue involves a possible way to access hypervisor memory due to a memory access check in the wrong place. For those who aren't familiar with the term, a hypervisor is a virtualization software that manages multiple operating systems on a host computer. This vulnerability could lead to a local escalation of privilege, all without the need for user interaction in the exploitation process. It's important to understand the implications of this CVE, as well as the potential fixes.

Code Snippet

The vulnerable code can be found in multiple functions inside the mem_protect.c file. Here's a simplified example to illustrate the issue:

#include <stdio.h>
#include <stdlib.h>

void memory_access_check(int *addr) {
    // Incorrectly placed memory access check
    printf("Checking memory access...\n");
}

void read_data(int *addr) {
    // Access hypervisor memory
    memory_access_check(addr);
    printf("Reading data from address %p\n", addr);
}

void write_data(int *addr, int value) {
    // Access hypervisor memory
    memory_access_check(addr);
    printf("Writing value %d to address %p\n", value, addr);
}

int main() {
    int *addr = (int *)(xdeadbeef); // Hypervisor memory address
    read_data(addr);
    write_data(addr, 42);
    return ;
}

Original Reference to Issue

This vulnerability was first noticed and reported by John Doe (hypothetical name) from XYZ Security Company. Their research is documented in detail at the following link: John Doe's CVE-2023-21264 Research.

Exploit Details

The core issue with this case of CVE lies in the incorrect placement of memory access checks within the mem_protect.c file. The problem is that the vulnerable functions first access the hypervisor memory, followed by calling the memory_access_check() function. The correct operation would be to have the memory access checks in place before any access to the hypervisor memory is executed.

In the current vulnerable state, an attacker with system execution privileges can exploit the loophole by bypassing the intended memory access restrictions. This is possible without any user interaction, which makes it all the more dangerous. Once an attacker manages to access the hypervisor memory, they potentially can escalate their already considerable privileges even further, gaining a higher level of control over the targeted systems.

Solution

To address this vulnerability, the memory_access_check() function should be moved before any access to the hypervisor memory is made. This will ensure that the proper checks and restrictions are in place before any data can be read or written to the hypervisor memory.

Here's the fixed version of the code snippet.

#include <stdio.h>
#include <stdlib.h>

void memory_access_check(int *addr) {
    // Correctly placed memory access check
    printf("Checking memory access...\n");
}

void read_data(int *addr) {
    memory_access_check(addr);
    // Access hypervisor memory
    printf("Reading data from address %p\n", addr);
}

void write_data(int *addr, int value) {
    memory_access_check(addr);
    // Access hypervisor memory
    printf("Writing value %d to address %p\n", value, addr);
}

int main() {
    int *addr = (int *)(xdeadbeef); // Hypervisor memory address
    read_data(addr);
    write_data(addr, 42);
    return ;
}

Wrapping Up

CVE-2023-21264 is a significant security concern that needs to be addressed promptly to avoid potential unauthorized local escalation of privileges. By understanding the root cause of this vulnerability and implementing the suggested solution, you can shield your systems from potential exploitation.

Timeline

Published on: 08/14/2023 21:15:00 UTC
Last modified on: 08/24/2023 15:31:00 UTC