CVE-2025-68471
📋 TL;DR
This vulnerability allows remote attackers to crash the Avahi daemon by sending two specially crafted mDNS announcements with CNAME records two seconds apart. This affects systems running Avahi 0.9-rc2 and earlier versions, primarily Linux systems using Avahi for local network service discovery.
💻 Affected Systems
- Avahi
📦 What is this software?
Avahi by Avahi
Avahi by Avahi
⚠️ Risk & Real-World Impact
Worst Case
Denial of service on the Avahi daemon, disrupting local network service discovery and potentially affecting dependent services.
Likely Case
Temporary service disruption requiring daemon restart, causing brief loss of mDNS/DNS-SD functionality.
If Mitigated
Minimal impact with proper network segmentation and Avahi service isolation.
🎯 Exploit Status
Exploit requires sending two crafted packets with specific timing. Proof of concept is available in the GitHub advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after commit 9c6eb53bf2e290aed84b1f207e3ce35c54cc0aa1
Vendor Advisory: https://github.com/avahi/avahi/security/advisories/GHSA-56rf-42xr-qmmg
Restart Required: Yes
Instructions:
1. Update Avahi to latest version from distribution repositories. 2. For source builds: apply commit 9c6eb53bf2e290aed84b1f207e3ce35c54cc0aa1. 3. Restart avahi-daemon service.
🔧 Temporary Workarounds
Disable Avahi service
linuxStop and disable the Avahi daemon if not needed
sudo systemctl stop avahi-daemon
sudo systemctl disable avahi-daemon
Network filtering
linuxBlock mDNS traffic (port 5353/udp) at network boundaries
sudo iptables -A INPUT -p udp --dport 5353 -j DROP
🧯 If You Can't Patch
- Implement network segmentation to isolate Avahi services
- Monitor for avahi-daemon crashes and implement automatic restart
🔍 How to Verify
Check if Vulnerable:
Check Avahi version: avahi-daemon --version. If version is 0.9-rc2 or earlier, system is vulnerable.Check Version:
avahi-daemon --version 2>/dev/null || dpkg -l | grep avahi || rpm -qa | grep avahiVerify Fix Applied:
Verify version is newer than 0.9-rc2 and check if commit 9c6eb53bf2e290aed84b1f207e3ce35c54cc0aa1 is included.📡 Detection & Monitoring
Log Indicators:
- Avahi daemon crash logs in systemd journal
- Segmentation fault messages in /var/log/syslog
Network Indicators:
- Multiple mDNS announcements with CNAME records from single source
- Unusual port 5353/udp traffic patterns
SIEM Query:
source="syslog" AND "avahi-daemon" AND ("segmentation fault" OR "crash" OR "SIGSEGV")