CVE-2023-50434
📋 TL;DR
CVE-2023-50434 is a stack-based buffer over-read vulnerability in emdns's emdns_resolve_raw function that occurs when processing DNS requests. Remote attackers can exploit this by sending specially crafted DNS requests to the emdns server, potentially leading to information disclosure or remote code execution. Systems running vulnerable versions of emdns that accept DNS requests are affected.
💻 Affected Systems
- emdns
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, or use as a pivot point in network attacks.
Likely Case
Information disclosure through memory leaks, potential denial of service through application crashes, or limited code execution depending on system protections.
If Mitigated
Application crash or denial of service with proper memory protections (ASLR, DEP) limiting code execution possibilities.
🎯 Exploit Status
Exploitation requires sending DNS requests to the vulnerable service. The CVSS 9.8 score indicates critical severity with network-accessible attack vector.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after fbd1eef with proper null termination checks
Vendor Advisory: https://papers.mathyvanhoef.com/esorics2024.pdf
Restart Required: Yes
Instructions:
1. Update emdns to a version after fbd1eef with the fix. 2. Rebuild from source if using source distribution. 3. Restart the emdns service after updating.
🔧 Temporary Workarounds
Network Segmentation
linuxRestrict access to emdns service using firewall rules to only trusted networks
iptables -A INPUT -p udp --dport 53 -s trusted_network -j ACCEPT
iptables -A INPUT -p udp --dport 53 -j DROP
Service Disablement
linuxTemporarily disable emdns service if not required
systemctl stop emdns
systemctl disable emdns
🧯 If You Can't Patch
- Implement strict network access controls to limit who can send DNS requests to the emdns service
- Monitor for abnormal DNS request patterns and implement rate limiting on DNS queries
🔍 How to Verify
Check if Vulnerable:
Check emdns version and commit hash. If using source, verify if code contains the vulnerable emdns_resolve_raw function without proper null termination checks.Check Version:
emdns --version or check package manager (apt list --installed | grep emdns, yum list installed | grep emdns)Verify Fix Applied:
Verify emdns version is after fbd1eef or check source code for proper null termination in emdns_resolve_raw function.📡 Detection & Monitoring
Log Indicators:
- Application crashes of emdns process
- Abnormal memory access errors in system logs
- Unusual DNS query patterns
Network Indicators:
- DNS requests with malformed or unusually long domain names
- Multiple rapid DNS queries from single sources
SIEM Query:
source="emdns.log" AND ("segmentation fault" OR "buffer over-read" OR "memory violation")