CVE-2021-46310

What it actually does

Processing of specially crafted IW44 image data in IW44Image.cpp triggers a division by zero, resulting in an application crash and denial of service.

Why it matters to the business

Applications using this library become unavailable when users open or process malicious image files, leading to service interruptions and potential loss of productivity for users handling DJVU content.

How an attack unfolds

An attacker crafts a malformed DJVU file containing IW44 data designed to cause division by zero during parsing. The file is delivered to the target application via network or file share. Upon processing with djvulibre, the library encounters the zero divisor and crashes. Public exploits are available, increasing the likelihood of automated attacks despite low EPSS.

How to fix it

Upgrade djvulibre to the latest available version that resolves the divide-by-zero condition in IW44Image.cpp. Where no fixed release exists, implement sandboxing or input validation wrappers around image processing. Disable support for untrusted DJVU files until a patch is applied.

How to confirm the fix worked

Test the library against known crashing IW44 payloads to confirm absence of division by zero. Monitor process stability under malformed input and review source for safe division guards in IW44Image.cpp.

Typical attack path

1. Craft malicious DJVU image embedding IW44 data with zero divisor values
2. Deliver the file to the victim via email, web download, or shared storage
3. Victim application or service invokes djvulibre to parse or render the image
4. Division by zero occurs in IW44Image.cpp causing immediate process termination

How to detect it

Monitor application and system logs for segmentation faults, aborts, or crashes occurring during djvulibre image parsing. Correlate spikes in image-processing failures with user-reported unavailability of services handling DJVU files.

What your security team should do

• Immediately evaluate and apply any upstream patches for djvulibre
• Restrict processing of untrusted DJVU or IW44 content until mitigated
• Add crash monitoring and alerting for djvulibre-related processes
• Review and reduce dependency on the affected library where possible