CVE-2023-4863: Critical Heap Buffer Overflow Vulnerability in WebP in Google Chrome Exploitation and Mitigation Details

CVE-2023-4863 is a critical security vulnerability discovered in Google Chrome, specifically tied to the processing of WebP images. This vulnerability is classified as a heap buffer overflow, which could potentially allow a remote attacker to perform an out-of-bounds memory write operation via a malicious HTML page. The affected versions of Google Chrome are prior to 116..5845.187, and the issue has been addressed in the latest version. In this post, we will dive into the details of this vulnerability, including the root cause, exploit, and potential mitigation steps.

Overview

The issue resides in the WebP image format implementation in Google Chrome. WebP is a modern image format developed by Google, providing superior compression and quality characteristics compared to traditional formats like JPEG and PNG. However, a coding error in the handling of WebP images leads to a heap buffer overflow vulnerability, and consequently, a remote attacker could exploit this to execute arbitrary code or cause denial of service by sending a maliciously crafted HTML page to the target victim.

Details

The vulnerability stems from an incorrect calculation of the size of a buffer in the WebP image processing code. When Google Chrome tries to decompress and render a WebP image, it allocates memory based on the dimensions of the image (width and height). However, due to a programming error, it underestimates the required memory allocation, causing an adjacent heap buffer in the memory to become overwritten.

Here's a simplified code snippet illustrating the vulnerability

void process_webp_image(uint8_t* input_data, uint32_t width, uint32_t height) {
    uint32_t buffer_size = width * height; // incorrect memory calculation
    uint8_t* output_buffer = malloc(buffer_size); // allocate memory for the output image

    // Actual decompression and processing code
    ...
}

The buffer_size variable is used to determine the required memory to store the decompressed WebP image. However, the actual size calculation should account for the number of color channels (usually 3 or 4) in the image:

uint32_t buffer_size = width * height * num_channels; // correct memory calculation

Exploit

As a result of this flaw, an attacker could craft a special WebP image and embed it in a malicious HTML page. When a victim opens the HTML page using a vulnerable version of Google Chrome, the vulnerable code will be executed, and the attacker could potentially overwrite the adjacent memory, eventually leading to arbitrary code execution or a crash.

It is important to note that the details of exploiting this vulnerability in practice are more complex, and the attacker would need to carefully craft the content of the malicious WebP image to achieve control over the computer system. As a responsible disclosure, we won't be providing explicit examples of exploitation techniques.

Mitigation

Google has addressed the CVE-2023-4863 vulnerability in the release of Google Chrome 116..5845.187, and users should update to the latest version as soon as possible. As a general practice, it is essential to keep your software updated to the latest patch level to protect against security vulnerabilities and threats.

Conclusion

CVE-2023-4863 is a critical heap buffer overflow vulnerability affecting Google Chrome's handling of WebP images. By exploiting this vulnerability, a remote attacker could potentially execute arbitrary code or cause a denial of service on the victim's computer. It is crucial to update your Google Chrome browser to the latest version, 116..5845.187, to mitigate this issue.

Original References

1. Chromium Security Bulletin
2. NVD - CVE-2023-4863
3. WebP Image Format

Timeline

Published on: 09/12/2023 15:15:00 UTC
Last modified on: 09/18/2023 17:48:00 UTC