CVE-2020-7467
📋 TL;DR
This vulnerability in FreeBSD's bhyve hypervisor allows guest virtual machines to execute certain AMD virtualization instructions that bypass nested page table translation, potentially accessing host physical memory. It affects FreeBSD systems running bhyve with AMD SVM virtualization. Attackers with guest VM access could potentially read or modify host memory.
💻 Affected Systems
- FreeBSD bhyve hypervisor
📦 What is this software?
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Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
Freebsd by Freebsd
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⚠️ Risk & Real-World Impact
Worst Case
Guest VM escape leading to full host compromise, allowing attackers to access other VMs, host data, and potentially pivot to other systems.
Likely Case
Guest VM memory corruption or information disclosure, potentially leading to privilege escalation within the host environment.
If Mitigated
Limited impact if proper network segmentation and VM isolation are implemented, though host memory exposure remains possible.
🎯 Exploit Status
Exploitation requires guest VM access and knowledge of AMD virtualization instructions. No public exploits known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FreeBSD 12.2-STABLE r365767+, 11.4-STABLE r365769+, 12.1-RELEASE p10+, 11.4-RELEASE p4+, 11.3-RELEASE p14+
Vendor Advisory: https://security.FreeBSD.org/advisories/FreeBSD-SA-20:29.bhyve_svm.asc
Restart Required: Yes
Instructions:
1. Update FreeBSD using freebsd-update fetch && freebsd-update install
2. Rebuild world if using source: make buildworld && make installworld
3. Reboot the system
4. Verify bhyve service is properly restarted
🔧 Temporary Workarounds
Disable bhyve SVM
freebsdDisable AMD SVM virtualization support in bhyve configuration
sysctl hw.vmm.svm.disable=1
Restrict VM Access
allOnly allow trusted users/VMs on affected systems
🧯 If You Can't Patch
- Isolate affected virtualization hosts from sensitive networks
- Implement strict VM trust boundaries and monitor for unusual guest behavior
🔍 How to Verify
Check if Vulnerable:
Check FreeBSD version with 'uname -a' and compare to affected versions. Verify bhyve is installed and AMD SVM is enabled.Check Version:
uname -aVerify Fix Applied:
Verify version is patched with 'uname -a' showing patched version. Check sysctl hw.vmm.svm.disable if workaround applied.📡 Detection & Monitoring
Log Indicators:
- Unusual bhyve process behavior
- Guest VM attempting privileged operations
- Kernel panic or instability
Network Indicators:
- Unexpected network traffic from virtualization hosts
- Guest VMs accessing host-only networks
SIEM Query:
source="freebsd" AND (process="bhyve" AND (event="privileged_instruction" OR event="memory_access_violation"))