CVE-2025-47712
📋 TL;DR
A vulnerability in nbdkit's blocksize filter allows denial of service when clients request block status information for excessively large data ranges. This affects systems using nbdkit with the blocksize filter enabled. The flaw causes internal errors that crash or hang the service.
💻 Affected Systems
- nbdkit
📦 What is this software?
Nbdkit by Nbdkit Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for nbdkit service, disrupting all NBD (Network Block Device) operations and potentially affecting dependent services or virtual machines.
Likely Case
Service disruption requiring manual restart of nbdkit, causing temporary unavailability of block devices.
If Mitigated
Minimal impact if service is monitored and automatically restarted, though repeated attacks could cause availability issues.
🎯 Exploit Status
Exploitation requires sending specific malformed block status requests to nbdkit with blocksize filter enabled.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor-specific updates (e.g., nbdkit 1.38.1 or later for Red Hat)
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2025-47712
Restart Required: Yes
Instructions:
1. Update nbdkit package using system package manager. 2. For Red Hat: 'yum update nbdkit'. 3. For Debian/Ubuntu: 'apt update && apt upgrade nbdkit'. 4. Restart nbdkit services.
🔧 Temporary Workarounds
Disable blocksize filter
linuxRemove or disable the blocksize filter from nbdkit configurations if not required.
Edit nbdkit configuration to remove '--filter=blocksize' parameter
Limit client access
linuxRestrict nbdkit service to trusted clients only using firewall rules.
iptables -A INPUT -p tcp --dport 10809 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 10809 -j DROP
🧯 If You Can't Patch
- Implement network segmentation to isolate nbdkit services from untrusted networks.
- Deploy monitoring and automatic restart mechanisms for nbdkit services.
🔍 How to Verify
Check if Vulnerable:
Check if nbdkit is running with blocksize filter: 'ps aux | grep nbdkit | grep blocksize'Check Version:
nbdkit --versionVerify Fix Applied:
Check nbdkit version after update: 'nbdkit --version' and verify it's patched version📡 Detection & Monitoring
Log Indicators:
- nbdkit crash logs
- segmentation fault errors in system logs
- unexpected nbdkit service termination
Network Indicators:
- Unusual large block status requests to nbdkit port (default 10809)
- Sudden drop in nbdkit service availability
SIEM Query:
source="*nbdkit*" AND ("segmentation fault" OR "internal error" OR "crash")