CVE-2020-6071
📋 TL;DR
CVE-2020-6071 is a denial-of-service vulnerability in Videolabs libmicrodns 0.1.0 where improper handling of compressed labels in mDNS messages allows an attacker to cause infinite recursion and crash the service. This affects any system or application using the vulnerable libmicrodns library for multicast DNS functionality.
💻 Affected Systems
- Videolabs libmicrodns
📦 What is this software?
Libmicrodns by Videolabs
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of mDNS functionality, potentially affecting service discovery, device connectivity, and network operations that rely on mDNS.
Likely Case
Targeted mDNS service crashes requiring restart, causing temporary service disruption for affected applications.
If Mitigated
Minimal impact with proper network segmentation and updated software.
🎯 Exploit Status
Exploitation requires sending specially crafted mDNS packets to the vulnerable service. The vulnerability is well-documented with technical details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 0.2.0 and later
Vendor Advisory: https://github.com/videolabs/libmicrodns/releases
Restart Required: Yes
Instructions:
1. Update libmicrodns to version 0.2.0 or later. 2. Rebuild any applications using libmicrodns. 3. Restart affected services.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict mDNS traffic to trusted networks only
iptables -A INPUT -p udp --dport 5353 -s ! TRUSTED_NETWORK -j DROP
Disable mDNS
linuxDisable mDNS functionality if not required
systemctl stop avahi-daemon
systemctl disable avahi-daemon
🧯 If You Can't Patch
- Implement strict network filtering to block mDNS traffic from untrusted sources
- Monitor for mDNS service crashes and implement automated restart mechanisms
🔍 How to Verify
Check if Vulnerable:
Check libmicrodns version: dpkg -l | grep libmicrodns or rpm -qa | grep libmicrodnsCheck Version:
pkg-config --modversion libmicrodnsVerify Fix Applied:
Verify version is 0.2.0 or later: microdns --version📡 Detection & Monitoring
Log Indicators:
- Service crashes of mDNS-related processes
- Segmentation fault errors in system logs
Network Indicators:
- Unusual mDNS traffic patterns
- Multiple mDNS packets with compression pointers
SIEM Query:
source="systemd" AND "segmentation fault" AND ("microdns" OR "avahi")🔗 References
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-0994
- https://www.debian.org/security/2020/dsa-4671
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-0994
- https://www.debian.org/security/2020/dsa-4671
