CVE-2016-5824

What it actually does

A use-after-free vulnerability in libical allows an attacker to trigger memory corruption leading to a denial of service when processing a specially crafted ICS calendar file.

Why it matters to the business

Applications using libical to parse calendar files may crash unexpectedly when handling malicious input, disrupting services that rely on calendar data processing. Given its presence in multiple Linux distributions, widespread impact on enterprise systems is possible, though exploitation requires user interaction.

How an attack unfolds

An attacker crafts a malicious ICS file containing structures that cause use-after-free during parsing. The victim opens or processes the file in an application using libical, leading to a crash.

How to fix it

Update libical to a patched version that resolves the use-after-free issue. Monitor for updates in affected distributions like Ubuntu and Red Hat.

How to confirm the fix worked

Test parsing of known malicious ICS files to ensure no crash occurs. Check version of libical installed.

Typical attack path

1. Craft a malicious ICS file exploiting use-after-free
2. Deliver the file to the target (e.g., via email or download)
3. Victim opens the file in an affected application
4. Application crashes due to memory corruption

How to detect it

Look for application crashes or segmentation faults when processing ICS files in logs. Monitor for unexpected terminations in processes using libical.

What your security team should do

• Apply available updates for libical across all affected distributions
• Implement file scanning or sandboxing for ICS files if possible
• Monitor for crashes in applications using libical