CVE-2024-41928: bhyve Hypervisor Buffer Overflow RCE Vulnerability

CVE-2024-41928 Overview

CVE-2024-41928 is an out-of-bounds read vulnerability [CWE-125] in the FreeBSD bhyve hypervisor. Malicious code running inside a guest virtual machine can trigger a buffer overflow in the bhyve userspace process on the host. Successful exploitation yields arbitrary code execution in the context of bhyve, which typically runs as root. The bhyve process runs inside a Capsicum sandbox, so post-exploitation capabilities are constrained to those granted to the process. FreeBSD published advisory FreeBSD-SA-24:10.bhyve describing the flaw, and NetApp released NTAP-20240920-0009 covering affected products.

Critical Impact
A guest VM can escape isolation and execute code as root on the FreeBSD host, subject only to the Capsicum sandbox capabilities granted to bhyve.

Affected Products

FreeBSD (see FreeBSD-SA-24:10.bhyve for affected releases and patch levels)
NetApp products referenced in advisory NTAP-20240920-0009
Any hypervisor deployment using vulnerable versions of bhyve

Discovery Timeline

2024-09-05 - CVE-2024-41928 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-41928

Vulnerability Analysis

The flaw is an out-of-bounds read [CWE-125] in the bhyve userspace hypervisor process on FreeBSD. Guest-controlled input reaches a code path that reads beyond the intended buffer boundary. That read is coupled with follow-on processing that allows an attacker to convert the memory corruption into arbitrary code execution in the host process. Because bhyve typically runs as root, execution occurs with high privileges on the host, breaking the guest-host isolation boundary that hypervisor deployments rely on.

The Capsicum sandbox limits what the compromised bhyve process can do next. Capsicum restricts a process to capability-mode file descriptors and blocks most global namespace access. An attacker still gains full control over the compromised VM's host-side emulation process, its memory, and any capabilities delegated to it, including access to guest disk images and network interfaces attached to that guest.

Root Cause

The root cause is missing or insufficient bounds checking on data sourced from the guest VM before it is used to index into or read from a host-side buffer in bhyve. Consult FreeBSD-SA-24:10.bhyve for the specific affected device model or emulation subsystem and the exact code path patched.

Attack Vector

Exploitation requires code execution inside a guest VM running on a vulnerable bhyve host. No host-side authentication or user interaction is needed. The attacker crafts input through a guest device interface, such as an emulated PCI or storage device, that reaches the vulnerable parsing routine in bhyve. The attack vector is local to the virtualization boundary but remote from the perspective of a tenant-controlled guest against a shared host.

No public proof-of-concept is listed in the referenced advisories at time of writing. See the FreeBSD Security Advisory SA-24:10 for technical details on the affected code path.

Detection Methods for CVE-2024-41928

Indicators of Compromise

Unexpected crashes, restarts, or core dumps of the bhyve process on the host
bhyve child processes spawning unexpected executables or shells on the host
Unusual outbound network connections originating from the host bhyve process rather than the guest
Modifications to guest disk image files or host configuration files by the bhyve process outside of normal maintenance windows

Detection Strategies

Monitor host process telemetry for anomalous behavior of the bhyve process, including new child processes, unexpected system calls, and memory access patterns inconsistent with virtualization workloads
Enable and forward FreeBSD audit (auditd) events for bhyve process activity, including execve and file access outside declared VM image paths
Correlate guest instability, kernel panics, or device driver errors inside VMs with concurrent bhyve crashes on the host as a possible exploitation signal

Monitoring Recommendations

Centralize host and hypervisor logs in a SIEM and alert on bhyve process termination, restart loops, or Capsicum capability violations
Track host inventory to confirm all FreeBSD systems running bhyve have applied the patch level referenced in FreeBSD-SA-24:10.bhyve
Baseline normal bhyve resource usage and alert on deviations that could indicate exploitation attempts against emulated devices

How to Mitigate CVE-2024-41928

Immediate Actions Required

Apply the FreeBSD update described in FreeBSD-SA-24:10.bhyve to all hosts running bhyve
Restart affected virtual machines after patching so they load the fixed bhyve userspace binary
For NetApp deployments, review NetApp advisory NTAP-20240920-0009 and apply vendor-provided fixes
Inventory all multi-tenant or untrusted-guest bhyve hosts and prioritize them for patching

Patch Information

FreeBSD has published fixed releases and patches through advisory FreeBSD-SA-24:10.bhyve. Apply the errata patch using freebsd-update or rebuild from source per the advisory, then restart all guest VMs so they use the patched bhyve process. NetApp customers should follow guidance in NTAP-20240920-0009 for affected products.

Workarounds

Restrict guest VM workloads to trusted tenants until the host is patched, since exploitation requires code execution inside a guest
Verify that bhyve continues to run inside its Capsicum sandbox to limit blast radius if exploitation occurs
Segment bhyve hosts on isolated management networks to constrain lateral movement from a compromised hypervisor process
Disable or avoid attaching emulated devices that are not required by guest workloads, reducing the attack surface exposed to guests

bash

# Apply the FreeBSD errata update and restart affected VMs
freebsd-update fetch
freebsd-update install

# List running bhyve VMs, then stop and restart each to load the patched userspace
ps -ax | grep bhyve
# For each VM, stop the VM cleanly and restart it via your management tooling