CVE-2020-6079
📋 TL;DR
CVE-2020-6079 is a memory leak vulnerability in libmicrodns 0.1.0 that allows denial-of-service attacks via resource exhaustion. An attacker can repeatedly send malformed mDNS messages to trigger the vulnerability during domain name decoding. Systems using vulnerable versions of libmicrodns for mDNS services are affected.
💻 Affected Systems
- libmicrodns
📦 What is this software?
Libmicrodns by Videolabs
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of mDNS-dependent applications through memory exhaustion, potentially causing system instability or crashes.
Likely Case
Degraded performance or temporary unavailability of mDNS services, affecting service discovery and network functionality.
If Mitigated
Minimal impact with proper network segmentation and monitoring; services remain available with potential performance degradation.
🎯 Exploit Status
Exploitation requires network access to mDNS service (port 5353 UDP). The vulnerability is triggered by sending specially crafted mDNS packets repeatedly.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.2.0 and later
Vendor Advisory: https://github.com/videolabs/libmicrodns/releases
Restart Required: Yes
Instructions:
1. Upgrade libmicrodns to version 0.2.0 or later. 2. Rebuild any applications linked against libmicrodns. 3. Restart affected services using mDNS functionality.
🔧 Temporary Workarounds
Network Filtering
linuxBlock external mDNS traffic at network perimeter to prevent exploitation from untrusted networks.
iptables -A INPUT -p udp --dport 5353 -j DROP
Service Restriction
allConfigure mDNS services to only listen on necessary interfaces and restrict to trusted networks.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate mDNS services from untrusted networks
- Deploy memory monitoring and alerting for processes using libmicrodns to detect potential exploitation
🔍 How to Verify
Check if Vulnerable:
Check libmicrodns version: 'pkg-config --modversion libmicrodns' or check package manager for version 0.1.0Check Version:
pkg-config --modversion libmicrodns || dpkg -l | grep libmicrodns || rpm -qa | grep microdnsVerify Fix Applied:
Verify libmicrodns version is 0.2.0 or later and test mDNS functionality remains operational📡 Detection & Monitoring
Log Indicators:
- Memory usage spikes in mDNS-related processes
- Repeated mDNS parsing errors or failures
Network Indicators:
- High volume of mDNS traffic from single source
- Malformed mDNS packets targeting port 5353
SIEM Query:
source_port=5353 AND (packet_size>900 OR protocol_anomaly=true)🔗 References
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-1002
- https://www.debian.org/security/2020/dsa-4671
- https://security.gentoo.org/glsa/202005-10
- https://talosintelligence.com/vulnerability_reports/TALOS-2020-1002
- https://www.debian.org/security/2020/dsa-4671
