CVE-2020-6077
📋 TL;DR
CVE-2020-6077 is an out-of-bounds read vulnerability in Videolabs libmicrodns 0.1.0 that allows remote attackers to cause denial of service by sending specially crafted mDNS messages. The vulnerability affects systems using this library for multicast DNS functionality. Attackers can crash affected services without authentication.
💻 Affected Systems
- Videolabs libmicrodns
📦 What is this software?
Libmicrodns by Videolabs
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of mDNS-dependent applications, potentially affecting service discovery, zero-configuration networking, and IoT device communication.
Likely Case
Service crashes requiring manual restart, disrupting local network service discovery and device communication.
If Mitigated
Minimal impact with proper network segmentation and updated software.
🎯 Exploit Status
Exploitation requires sending specially crafted mDNS packets to vulnerable systems. The vulnerability is well-documented with public technical details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 0.2.0 or 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 applications using the library. 3. Restart affected services.
🔧 Temporary Workarounds
Network segmentation
linuxRestrict mDNS traffic to trusted network segments using firewall rules.
iptables -A INPUT -p udp --dport 5353 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p udp --dport 5353 -j DROP
Disable mDNS services
linuxDisable mDNS functionality if not required.
systemctl stop avahi-daemon
systemctl disable avahi-daemon
🧯 If You Can't Patch
- Implement strict network segmentation to isolate mDNS traffic
- Monitor for abnormal mDNS traffic patterns and service crashes
🔍 How to Verify
Check if Vulnerable:
Check if libmicrodns 0.1.0 is installed: 'ldconfig -p | grep microdns' or check package manager.Check Version:
pkg-config --modversion libmicrodns || ldconfig -p | grep microdnsVerify Fix Applied:
Verify libmicrodns version is 0.2.0 or later: 'pkg-config --modversion libmicrodns'📡 Detection & Monitoring
Log Indicators:
- Service crashes related to mDNS
- Segmentation fault errors in application logs
- Abnormal termination of mDNS services
Network Indicators:
- Unusual mDNS traffic patterns
- Malformed mDNS packets
- High volume of mDNS requests
SIEM Query:
source="*mdns*" AND (event="crash" OR event="segfault" OR event="abnormal_termination")🔗 References
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-1000
- https://www.debian.org/security/2020/dsa-4671
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-1000
- https://www.debian.org/security/2020/dsa-4671
