CVE-2022-0635
📋 TL;DR
CVE-2022-0635 is a denial-of-service vulnerability in BIND 9.18.0 where specific DNS queries can trigger an assertion failure, causing the named process to terminate. This affects organizations running vulnerable BIND versions as DNS servers. The vulnerability allows attackers to crash DNS services, disrupting name resolution.
💻 Affected Systems
- ISC BIND
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete DNS service outage across all zones served by the vulnerable BIND instance, potentially affecting all dependent services and applications.
Likely Case
Intermittent DNS service disruptions affecting clients relying on the vulnerable server for name resolution.
If Mitigated
Minimal impact with proper network segmentation, rate limiting, and monitoring in place to detect and respond to attack attempts.
🎯 Exploit Status
Exploitation requires sending specific DNS queries but does not require authentication. The vulnerability is well-documented in public advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.18.1 or later
Vendor Advisory: https://kb.isc.org/v1/docs/cve-2022-0635
Restart Required: Yes
Instructions:
1. Download BIND 9.18.1 or later from ISC. 2. Stop the named service. 3. Install the updated version. 4. Restart the named service. 5. Verify the service is running correctly.
🔧 Temporary Workarounds
Rate Limiting
allImplement DNS query rate limiting to reduce the impact of attack attempts
# Add to named.conf options section:
rate-limit {
responses-per-second 10;
window 5;
};
Query Filtering
allUse ACLs to restrict which clients can query the DNS server
# Add to named.conf:
acl trusted-clients { 192.168.1.0/24; };
options {
allow-query { trusted-clients; };
};
🧯 If You Can't Patch
- Implement strict network ACLs to limit DNS queries to trusted sources only
- Deploy additional DNS servers for redundancy and load balancing to maintain service during attacks
🔍 How to Verify
Check if Vulnerable:
Check BIND version with: named -v | grep '^BIND'Check Version:
named -vVerify Fix Applied:
Verify version is 9.18.1 or later: named -v | grep '^BIND 9.18.[1-9]'📡 Detection & Monitoring
Log Indicators:
- named process termination/crash logs
- Assertion failure messages in BIND logs
- Increased error rates in DNS query logs
Network Indicators:
- Unusual patterns of DNS queries from single sources
- DNS service unavailability alerts
SIEM Query:
source="bind" AND ("assertion failure" OR "named exiting" OR "SIGABRT")