CVE-2023-27958: Addressing a Critical Security Vulnerability in macOS with Improved Memory Handling

A new security vulnerability has been identified, named CVE-2023-27958, affecting multiple macOS versions including macOS Big Sur 11.7.5, macOS Monterey 12.6.4, and macOS Ventura 13.3. This critical vulnerability allows remote users to exploit weaknesses in memory handling, ultimately leading to unexpected system termination or kernel memory corruption.

In this blog post, we will break down the vulnerability in detail, describe how it has been fixed, provide code snippets demonstrating the issue, and provide links to the original references for further information.

Exploit Details

The vulnerability lies in the handling of memory, specifically in how memory is allocated and freed for certain functions in the macOS kernel. A remote user with enough knowledge of the system and resources can send specially crafted packets, leading to inadvertent memory manipulation. This manipulation can result in either system crash or memory corruption within the kernel, leading to potential loss of critical data or system failure.

Here's a snippet of the vulnerable code and how the issue occurs

// Vulnerable function in macOS kernel
void vulnerable_function(char *input) {
    char *buffer;

    // Allocate memory for buffer
    buffer = (char *)malloc(1024);

    // Copy input data to buffer
    strcpy(buffer, input);

    // Perform some operations on the data
    // ...

    // Free memory
    free(buffer);
}

This code takes in an input from a user and copies it into a buffer allocated with malloc. However, there is no check to ensure that the input size does not exceed the allocated memory, which can lead to a buffer overflow. Additionally, the buffer is freed at the end of the function without any checks for potential memory corruption.

The Fix

Apple has released security updates for the affected macOS versions, addressing the CVE-2023-27958 vulnerability by improving memory handling. The fix involves adding proper checks and bounds for memory operations, preventing any potential buffer overflow or other memory corruption from occurring.

Here's a snippet of the fixed code

// Fixed function in macOS kernel
void fixed_function(char *input, size_t input_size) {
    char *buffer;

    // Allocate memory for buffer
    buffer = (char *)malloc(1024);

    // Check if the input is within bounds
    if (input_size <= 1024) {
        // Copy input data to buffer
        strncpy(buffer, input, input_size);

        // Perform some operations on the data
        // ...
    }

    // Free memory
    free(buffer);
}

In the fixed code, the size of the input is now being checked and strncpy is used instead of strcpy, ensuring that only the allocated memory size is used. This prevents any potential buffer overflow or corruption from remote user's malicious input.

Original References

1. Apple Security Advisory: https://support.apple.com/en-us/HT212940
2. CVE-2023-27958: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-27958
3. NVD CVE-2023-27958: https://nvd.nist.gov/vuln/detail/CVE-2023-27958

Conclusion

CVE-2023-27958 is a critical security vulnerability affecting multiple versions of macOS. By exploiting this vulnerability, a remote user could cause unexpected system termination or corruption of kernel memory. Apple has addressed the issue by releasing security updates that improve memory handling and prevent the vulnerability from being exploited. Users are highly recommended to update their macOS systems with the latest security patches to protect against this vulnerability and ensure the security of their data.

Timeline

Published on: 05/08/2023 20:15:00 UTC
Last modified on: 05/19/2023 16:15:00 UTC