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Overview

If you work with images in any kind of automated workflow, libraries like Accusoft ImageGear can be crucial for reading, editing, or generating files. But what if a simple picture could let an attacker take over your system? In this post, we dive deep into CVE-2022-32588, a serious flaw in ImageGear 20. that allows an attacker to corrupt memory using a specially crafted file. The root cause lies within the PICT image format parser, specifically the pctwread_14841 function.

It affects the PICT file format parser inside Accusoft’s ImageGear 20. library.

- Attackers can create a malicious PICT image file that, when opened or processed, can corrupt memory and potentially execute code.

Why Does This Matter?

- Image processing often happens in the background: think apps that auto-generate thumbnails, security cameras, or insurance claim systems.

Where’s the Bug?

The vulnerability lives in the function that reads and interprets PICT data blocks — specifically, pctwread_14841. It fails to properly check boundaries before writing to memory.

What’s an Out-of-Bounds Write?

This just means the code writes somewhere outside the allocated buffer. This can overwrite nearby variables, function pointers, or critical data, resulting in:

Reference: Code Walkthrough

While the exact source code for proprietary ImageGear isn’t published, security researchers reverse-engineered enough to make this possible PoC (Proof of Concept):

// Pseudocode approximation of vulnerable logic
uint8_t buffer[256];
// size read from file, but not checked!
uint16_t size = read_uint16_from_file(f); 
for (int i = ; i < size; i++) {
    buffer[i] = getc(f); // No boundary check => overflow
}

If size is bigger than 256, any data gets written beyond buffer, causing an out-of-bounds write.

Malicious File Example

Attackers craft a PICT file where the length field is large (x100 for example), but the image is small—tricking the code into writing way past what was expected.

How Can Attackers Exploit This?

1. Create: Use a hex editor or exploit framework to craft a malformed PICT file with an oversized length field.
2. Deliver: Submit/upload the file to a web app or service that uses ImageGear for processing (e.g., image preview, document processing).
3. Trigger: When the back-end or user processes the file, the overflow happens, allowing the attacker to crash the service or potentially run arbitrary code.

Proof of Concept: Generating a Malformed PICT File

Want to see it in action? Here’s a Python script that generates a pseudo-malicious PICT file to trigger the bug:

# WARNING: Don't open this file with vulnerable software!
with open("malicious.pict", "wb") as f:
    f.write(b'\x00\x11\x02')     # PICT header (sample)
    f.write((4096).to_bytes(2, 'big')) # Big size field!
    f.write(b'A' * 4096)         # Junk data, overflows buffer

Real World Impact

- Any server or desktop application that accepts user-supplied images and uses the vulnerable ImageGear library can be compromised.

Mitigation & Fixes

- Upgrade: Accusoft released ImageGear 20.1+, which fixes this bug by properly validating input sizes.

Additional References

- Accusoft Security Advisory
- CVE Record: CVE-2022-32588
- ZDI Advisory (Zero Day Initiative)

Conclusion

CVE-2022-32588 shows how even a simple image file can open the gates to attackers when parsers aren’t careful. If you’re running any software that relies on Accusoft ImageGear to process user-supplied images, patch immediately — and consider isolating your image processing pipeline from your critical systems.

> Safety tip: Always treat images as potentially dangerous — just like PDFs or executables.

Timeline

Published on: 11/09/2022 18:15:00 UTC
Last modified on: 11/10/2022 06:46:00 UTC