CVE-2020-12761

What it actually does

Integer overflow in the ICO color map parser leads to undersized allocations followed by out-of-bounds reads when loading crafted icon files.

Why it matters to the business

Applications that render user-supplied icons can crash or leak memory contents, potentially exposing sensitive data or causing service outages in image-processing pipelines.

How an attack unfolds

An attacker creates an ICO file whose color-map count triggers the integer overflow during allocation; the resulting undersized buffer is then read past its bounds when the loader populates pixel data, allowing information disclosure or denial of service.

How to fix it

Upgrade imlib2 to a version containing the corrected loader_ico.c logic; if no newer package is available, disable ICO support or sandbox the image-processing component.

How to confirm the fix worked

Confirm the installed imlib2 version is newer than 1.6.0 and that the loader rejects oversized color maps; fuzz or replay the original proof-of-concept ICO to verify absence of crashes or leaks.

Typical attack path

1. Craft a malicious ICO file containing an excessively large color-map count
2. Deliver the file to any process that invokes imlib2's ICO loader (web upload, email attachment, document preview)
3. Trigger image loading via normal application flow
4. Observe process crash or extract leaked memory from the out-of-bounds read

How to detect it

Monitor application logs for segmentation faults or memory-allocation failures immediately after ICO file handling; inspect process core dumps for evidence of oversized color-map processing.

What your security team should do

• Inventory all systems and containers that link against imlib2 and schedule upgrades
• Add imlib2 version checks to vulnerability scanning policies
• Restrict untrusted image formats where possible until patches are deployed