CVE-2024-51563
📋 TL;DR
This CVE describes a time-of-check to time-of-use (TOCTOU) race condition in the virtio_vq_recordon function in bhyve's virtual I/O implementation. It allows a malicious guest VM to potentially crash the host system or execute arbitrary code on the host. Affected systems include FreeBSD installations running bhyve virtualization with vulnerable versions.
💻 Affected Systems
- FreeBSD bhyve hypervisor
⚠️ 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
A malicious guest VM could achieve arbitrary code execution on the host system, potentially compromising the entire virtualization infrastructure and all other VMs.
Likely Case
Guest VM could cause a host kernel panic or denial of service, crashing the hypervisor and disrupting all virtual machines.
If Mitigated
With proper isolation and minimal guest privileges, impact would be limited to denial of service affecting only the attacking VM.
🎯 Exploit Status
Exploitation requires guest VM access and knowledge of race condition timing. No public exploits have been reported as of the advisory date.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FreeBSD 14.1-RELEASE-p2, FreeBSD 14.2-RELEASE-p1, FreeBSD 15.0-RELEASE-p1
Vendor Advisory: https://security.freebsd.org/advisories/FreeBSD-SA-24:17.bhyve.asc
Restart Required: Yes
Instructions:
1. Update FreeBSD system using 'freebsd-update fetch' and 'freebsd-update install'. 2. Rebuild world if using source-based updates. 3. Reboot the host system to load patched kernel.
🔧 Temporary Workarounds
Disable bhyve virtualization
FreeBSDTemporarily disable bhyve hypervisor if not required
kldunload vmm
echo 'vmm_load="NO"' >> /boot/loader.conf
🧯 If You Can't Patch
- Isolate bhyve hosts on separate network segments with strict access controls
- Implement strict monitoring of guest VM behavior and limit guest privileges
🔍 How to Verify
Check if Vulnerable:
Check FreeBSD version with 'uname -a' and compare against affected versions. Verify bhyve is loaded with 'kldstat | grep vmm'.Check Version:
uname -aVerify Fix Applied:
Verify FreeBSD version is patched with 'uname -a' showing p2/p1 suffix. Check that bhyve module loads without errors.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- bhyve process crashes
- Unexpected guest VM behavior
Network Indicators:
- Sudden loss of connectivity to multiple VMs
- Unusual guest VM network activity
SIEM Query:
source="kernel" AND ("panic" OR "bhyve crash")