CVE-2019-9748
📋 TL;DR
This vulnerability in tinysvcmdns allows attackers to read up to 16KB of arbitrary memory by sending crafted mDNS packets. This can cause server crashes via segmentation faults or lead to memory content disclosure through error messages. Anyone using tinysvcmdns through version 2018-01-16 is affected.
💻 Affected Systems
- tinysvcmdns
📦 What is this software?
Tinysvcmdns by Tinysvcmdns Project
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise through memory disclosure leading to credential theft, followed by denial of service via segmentation fault crashes.
Likely Case
Server crashes causing denial of service, with potential memory disclosure revealing sensitive information.
If Mitigated
Limited impact if proper network segmentation and memory protection mechanisms are in place.
🎯 Exploit Status
Exploitation requires sending crafted mDNS packets to the vulnerable service. The vulnerability is well-documented in public issue trackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None
Vendor Advisory: https://bitbucket.org/geekman/tinysvcmdns/issues/10/arbitrary-memory-read-while-parsing
Restart Required: No
Instructions:
No official patch exists. The vendor states the project is unmaintained. Replace tinysvcmdns with an alternative mDNS implementation.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict access to mDNS service using firewall rules to limit exposure.
iptables -A INPUT -p udp --dport 5353 -s trusted_network -j ACCEPT
iptables -A INPUT -p udp --dport 5353 -j DROP
Service Disablement
linuxDisable the tinysvcmdns service if not required.
systemctl stop tinysvcmdns
systemctl disable tinysvcmdns
🧯 If You Can't Patch
- Replace tinysvcmdns with maintained alternative like Avahi or Apple's mDNSResponder
- Implement strict network ACLs to limit mDNS traffic to trusted sources only
🔍 How to Verify
Check if Vulnerable:
Check if tinysvcmdns is installed and running: ps aux | grep tinysvcmdns and check version in source code or documentation.Check Version:
No standard version command. Check source code headers or installation documentation for version information.Verify Fix Applied:
Verify tinysvcmdns is no longer running and has been replaced with alternative software.📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in system logs
- Unexpected mDNS packet parsing errors
- Service crash/restart events
Network Indicators:
- Unusual mDNS traffic patterns
- Crafted mDNS packets to port 5353
SIEM Query:
source="systemd" AND "tinysvcmdns" AND ("segmentation fault" OR "crash")