CVE-2025-8677
📋 TL;DR
A denial-of-service vulnerability in BIND DNS servers where querying a specially crafted zone containing malformed DNSKEY records causes CPU exhaustion, potentially crashing the server. This affects BIND 9 versions 9.18.0-9.18.39, 9.20.0-9.20.13, 9.21.0-9.21.12, and corresponding subscription versions. Organizations running vulnerable BIND instances as authoritative or recursive resolvers are at risk.
💻 Affected Systems
- ISC BIND
⚠️ 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
Complete DNS service outage due to CPU exhaustion causing BIND process crash, disrupting all DNS resolution for dependent services and clients.
Likely Case
Degraded DNS performance with high CPU usage leading to slow query responses and potential service instability.
If Mitigated
Minimal impact with proper network segmentation and query rate limiting preventing exploitation attempts.
🎯 Exploit Status
Exploitation requires sending DNS queries to vulnerable servers, which is trivial for network-accessible systems. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.18.40, 9.20.14, 9.21.13, and corresponding subscription versions
Vendor Advisory: https://kb.isc.org/docs/cve-2025-8677
Restart Required: Yes
Instructions:
1. Download patched version from ISC website or package repository. 2. Stop BIND service. 3. Install updated package. 4. Start BIND service. 5. Verify version and functionality.
🔧 Temporary Workarounds
Query Rate Limiting
allImplement query rate limiting to reduce impact of malicious queries
Add 'rate-limit { responses-per-second 10; };' to named.conf options
Access Control Restrictions
allRestrict which clients can query the server
Add 'allow-query { trusted-nets; };' to appropriate zones in named.conf
🧯 If You Can't Patch
- Implement network-level filtering to block queries from untrusted sources
- Deploy load balancers or DNS proxies in front of vulnerable servers to absorb attack traffic
🔍 How to Verify
Check if Vulnerable:
Check BIND version with 'named -v' or 'rndc status' and compare against affected versionsCheck Version:
named -vVerify Fix Applied:
Verify version is 9.18.40+, 9.20.14+, or 9.21.13+ and monitor CPU usage during normal operation📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU usage in system logs
- BIND process crashes or restarts
- Increased query volumes from single sources
Network Indicators:
- Spike in DNS queries to specific zones
- Unusual query patterns for DNSKEY records
SIEM Query:
source="bind" AND (cpu_usage>90 OR process="named" AND event="crash")