CVE-2024-46258 - Inside the Heap Buffer Overflow in cute_png v1.05 (cp_load_png

Recently, a vulnerability dubbed CVE-2024-46258 was discovered in the widely used header-only PNG decoding library cute_png, version 1.05. This critical flaw is a heap buffer overflow located within the cp_load_png_mem() function in cute_png.h. In this article, we’ll break down what this vulnerability actually is, how it might be exploited, share a code snippet you can try out, and explain how to secure your applications.

What Is cute_png?

cute_png is a header-only, lightweight C library that helps developers easily decode PNG images directly in their apps.

About the Vulnerability

CVE-2024-46258 is a heap buffer overflow. This means attackers can trick the library into writing more data than it should outside of the part of memory it owns (the heap), which often leads to crashes, unwanted code execution, or even the ability to take over the vulnerable program.

Vulnerable Function:

The root cause is in the following function

cp_image_t* cp_load_png_mem(const void* memory, int size);

This function loads PNG image data from a chunk of memory.

The Flawed Code

Here’s a simplified version (not the full code!) illustrating a typical heap buffer overflow pattern in cp_load_png_mem():

unsigned char* out = (unsigned char*)CUTE_PNG_MALLOC(bytes_needed);
...
// Decoding loop (snipped for brevity)
for (int y = ; y < height; ++y) {
    for (int x = ; x < width * 4; ++x) {
        // No bounds checks here!
        out[offset + x] = ... // Data copied from source to output
    }
    offset += pitch;
}

If a PNG file with corrupted or artificially crafted header fields (like super large width/height or invalid pitch calculation) is loaded, the program might allocate a smaller buffer but try to write way past its end, because there is no extra checking after allocation.

What can an attacker do?

An attacker may construct a malicious PNG file engineered to trigger this overflow. When your code tries to cp_load_png_mem() the evil PNG, the overflow may:

Crash your application, possibly opening a denial-of-service hole

This kind of flaw is a classic vector for remote code execution in software that processes untrusted images (like image servers, desktop tools, etc.).

Below is a conceptual PoC (do NOT use with real apps—for demonstration only!)

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

// Prepare a buffer with a crafted PNG (evil_png)...
unsigned char evil_png[] = { /* Evil PNG bytes here */ };
int evil_png_size = sizeof(evil_png);

int main() {
    cp_image_t* img = cp_load_png_mem(evil_png, evil_png_size);
    if (img) {
        printf("Image loaded!\n");
        // ... process image
        cp_free_png(img);
    } else {
        printf("Failed to load the image!\n");
    }
    return ;
}

The trick is to build evil_png so its headers cause cp_load_png_mem() to under-allocate the heap buffer, but later overflow the buffer during decoding.

Mitigation and Recommendations

- Upgrade: Watch for a patched version of cute_png, or update to the latest if available (the repo is active).
- Input Validation: Always validate or sanitize PNG files before processing. Reject freakishly large images or odd dimensions from untrusted sources.

Conclusion

The CVE-2024-46258 heap buffer overflow in cute_png is a serious vulnerability that could lead to crashes or even remote code execution. If your app lets users upload or interact with images and you use cute_png, patch ASAP, validate inputs, and stay tuned to updates from the author.

References

- https://nvd.nist.gov/vuln/detail/CVE-2024-46258
- https://github.com/RandyGaul/cute_png
- https://www.cve.org/CVERecord?id=CVE-2024-46258

Timeline

Published on: 10/01/2024 14:15:05 UTC
Last modified on: 10/04/2024 16:41:08 UTC

CVE-2024-46258 - Inside the Heap Buffer Overflow in cute_png v1.05 (cp_load_png_mem)