CVE-2017-6960

What it actually does

Integer overflow in load_apng allows attacker-controlled imagesize value to trigger a heap-based buffer over-read, resulting in memory access beyond allocated bounds and potential process crash.

Why it matters to the business

Organizations relying on apng2gif for image conversion pipelines face risk of service disruption when processing untrusted animated PNG files, with possible operational downtime in automated media workflows across Debian and Ubuntu deployments.

How an attack unfolds

An attacker crafts a malicious APNG file with an imagesize value engineered to overflow during load_apng processing; when the converter opens the file the overflow causes an oversized read that crashes the process without requiring authentication or user interaction.

How to fix it

Replace apng2gif with a maintained alternative or apply any available upstream patches; on Debian and Ubuntu systems ensure the package is removed or isolated from untrusted input sources until a fixed build is available.

How to confirm the fix worked

Test conversion of known-good and boundary-case APNG files in an isolated environment; monitor process stability and memory sanitizer output to confirm absence of over-read conditions after any package update or replacement.

Typical attack path

1. Identify target systems or pipelines that invoke apng2gif on untrusted input
2. Craft APNG file containing integer overflow trigger in imagesize field
3. Deliver file via network, upload, or email to reach conversion routine
4. Trigger conversion which executes load_apng and induces heap over-read crash

How to detect it

Review system and application logs for abrupt apng2gif process terminations or segmentation faults when processing APNG inputs; correlate with file upload or conversion timestamps to identify suspicious activity.

What your security team should do

• Remove or sandbox apng2gif from all automated image-processing workflows handling external files
• Scan package inventories on Debian and Ubuntu hosts to locate remaining instances
• Substitute with alternative conversion tools that receive ongoing security maintenance
• Add file-type validation and sandboxing for any remaining image conversion steps