CVE-2023-41173
📋 TL;DR
AdGuard DNS versions before 2.2 contain a vulnerability where remote attackers can send malformed UDP packets to cause denial of service. This affects all systems running vulnerable AdGuard DNS instances, potentially disrupting DNS resolution services.
💻 Affected Systems
- AdGuard DNS
📦 What is this software?
Adguard Dns by Adguard
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage of DNS resolution, affecting all downstream clients and services that rely on the vulnerable AdGuard DNS instance.
Likely Case
Intermittent DNS service disruption causing failed domain lookups and connectivity issues for clients.
If Mitigated
Minimal impact with proper network segmentation and rate limiting in place.
🎯 Exploit Status
Exploitation requires only the ability to send UDP packets to the vulnerable service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.2
Vendor Advisory: https://adguard-dns.io/en/versions.html#2.2
Restart Required: Yes
Instructions:
1. Download AdGuard DNS version 2.2 or later from official sources. 2. Stop the current AdGuard DNS service. 3. Install the updated version. 4. Restart the service.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict UDP access to AdGuard DNS instances using firewall rules.
iptables -A INPUT -p udp --dport 53 -j DROP
Rate Limiting
linuxImplement UDP packet rate limiting to reduce DoS impact.
iptables -A INPUT -p udp --dport 53 -m limit --limit 50/sec -j ACCEPT
🧯 If You Can't Patch
- Implement strict network ACLs to limit UDP traffic to trusted sources only.
- Deploy redundant DNS instances behind load balancers to maintain service during attacks.
🔍 How to Verify
Check if Vulnerable:
Check AdGuard DNS version using the service status command or configuration file.Check Version:
adguard-dns --versionVerify Fix Applied:
Confirm version is 2.2 or higher and test DNS resolution under UDP traffic.📡 Detection & Monitoring
Log Indicators:
- Unusual UDP packet volume
- Service restart logs
- DNS query timeouts
Network Indicators:
- Spike in malformed UDP packets to port 53
- Increased DNS response errors
SIEM Query:
source="adguard-dns" AND (event="service_restart" OR event="packet_error")