CVE-2016-9584
📋 TL;DR
CVE-2016-9584 is a use-after-free vulnerability in libical that allows remote attackers to cause denial of service and potentially read heap memory via a crafted ICS file. This affects any application that uses libical to parse calendar data, including email clients, calendar applications, and web services. The vulnerability could lead to application crashes or information disclosure.
💻 Affected Systems
- libical
- Applications using libical library (e.g., Evolution, Thunderbird with calendar features, various web calendar services)
📦 What is this software?
Libical by Libical Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, though this is less likely than denial of service.
Likely Case
Application crash (denial of service) and potential heap memory disclosure revealing sensitive information.
If Mitigated
Limited impact with proper input validation and memory protection mechanisms in place.
🎯 Exploit Status
Exploitation requires sending a crafted ICS file to a vulnerable application. Proof-of-concept code has been publicly disclosed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: libical 1.0 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1401958
Restart Required: Yes
Instructions:
1. Update libical package to version 1.0 or later using your distribution's package manager. 2. Restart any services or applications using libical. 3. Recompile any custom applications with the updated library.
🔧 Temporary Workarounds
Disable ICS file processing
allTemporarily disable parsing of ICS files in affected applications until patching is complete.
Application-specific configuration changes required
Input validation filtering
allImplement strict validation of ICS files before passing to libical parser.
Custom application code required
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Use application firewalls to block malicious ICS files
🔍 How to Verify
Check if Vulnerable:
Check libical version: `dpkg -l | grep libical` (Debian/Ubuntu) or `rpm -qa | grep libical` (RHEL/CentOS)Check Version:
libical-config --version or check package manager outputVerify Fix Applied:
Verify libical version is 1.0 or later using the same commands📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults
- Memory access violation errors in application logs
Network Indicators:
- Unexpected ICS file transfers to vulnerable services
SIEM Query:
source="application.log" AND ("segmentation fault" OR "use-after-free" OR "libical")