CVE-2020-23793
📋 TL;DR
This vulnerability in spice-server allows unauthorized restart of KVM virtual machines in Red Hat's VDI product. It affects systems running specific versions of spice-server on Red Hat Enterprise Linux 7.6.1. The vulnerability could disrupt virtual machine availability without proper authentication.
💻 Affected Systems
- Red Hat VDI product with spice-server
📦 What is this software?
Spice Server by Spice Space
⚠️ Risk & Real-World Impact
Worst Case
Attackers could repeatedly restart critical VMs causing sustained denial of service, disrupting business operations and potentially leading to data corruption or loss.
Likely Case
Unauthorized users restarting non-critical VMs causing temporary service disruption and operational impact.
If Mitigated
With proper network segmentation and access controls, impact limited to isolated VMs with minimal business disruption.
🎯 Exploit Status
The description indicates no authorization required, suggesting relatively straightforward exploitation once the attack vector is understood.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Red Hat Security Advisory for updated version
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2020-23793
Restart Required: Yes
Instructions:
1. Check current spice-server version. 2. Apply Red Hat security updates via yum update spice-server. 3. Restart affected services/VMs. 4. Verify patch installation.
🔧 Temporary Workarounds
Network segmentation
linuxRestrict network access to spice-server ports to authorized management networks only
iptables -A INPUT -p tcp --dport [spice-port] -s [trusted-network] -j ACCEPT
iptables -A INPUT -p tcp --dport [spice-port] -j DROP
Access control hardening
allImplement strict authentication and authorization controls for VDI management interfaces
🧯 If You Can't Patch
- Isolate affected systems from untrusted networks using firewall rules
- Implement monitoring for unauthorized VM restart attempts and alert on suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check spice-server version: rpm -q spice-serverCheck Version:
rpm -q spice-server --queryformat '%{VERSION}-%{RELEASE}\n'Verify Fix Applied:
Verify updated version: rpm -q spice-server | grep -v '0.14.0-6.el7_6.1'📡 Detection & Monitoring
Log Indicators:
- Unexpected VM restart events in libvirt/qemu logs
- Unauthorized connection attempts to spice-server ports
- Multiple VM restart events from single source
Network Indicators:
- Unusual traffic to spice-server default ports (typically 5900-5902)
- Connection attempts from unauthorized IP addresses
SIEM Query:
source="libvirt" OR source="qemu" AND (event="restart" OR event="shutdown") | stats count by src_ip, vm_name