CVE-2024-46739 in Linux
Summary
by MITRE • 09/18/2024
In the Linux kernel, the following vulnerability has been resolved:
uio_hv_generic: Fix kernel NULL pointer dereference in hv_uio_rescind
For primary VM Bus channels, primary_channel pointer is always NULL. This pointer is valid only for the secondary channels. Also, rescind callback is meant for primary channels only.
Fix NULL pointer dereference by retrieving the device_obj from the parent for the primary channel.
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Analysis
by VulDB Data Team • 04/05/2026
The vulnerability CVE-2024-46739 represents a critical kernel NULL pointer dereference in the Linux kernel's hypervisor user interface driver implementation. This issue specifically affects the uio_hv_generic module which handles UIO (User Space I/O) operations for Hyper-V virtualization environments. The flaw occurs within the hv_uio_rescind function where the system attempts to access a primary_channel pointer that is inherently NULL for primary VM Bus channels, creating a dangerous execution path that can lead to system crashes or potential privilege escalation.
The technical root cause stems from a fundamental misunderstanding of the channel hierarchy within Hyper-V's virtualization framework. Primary VM Bus channels operate differently from secondary channels, with primary_channel pointers being intentionally NULL for primary channels as they serve as the main communication pathways. However, the implementation incorrectly attempts to dereference this NULL pointer during the rescind callback operation, which is specifically designed to handle primary channels rather than secondary ones. This mismatch between expected behavior and actual implementation creates a direct path for kernel memory corruption when the rescind callback is invoked.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the entire virtualization environment. When a primary channel rescind event occurs, the kernel's handling of this event triggers the NULL pointer dereference, causing an immediate kernel oops and system instability. In virtualized environments, this could lead to complete VM crashes or even host system compromise if attackers can manipulate the timing or conditions under which the rescind callback is triggered. The vulnerability affects systems running Linux kernels that implement the uio_hv_generic driver and are configured to handle Hyper-V virtualization scenarios.
Mitigation strategies for CVE-2024-46739 require immediate kernel updates from vendors who have patched this specific NULL pointer dereference issue. Organizations should prioritize applying the latest security patches that properly handle the distinction between primary and secondary channel pointers in the hv_uio_rescind function. The fix implemented addresses the core issue by retrieving the device_obj from the parent channel for primary channels, eliminating the need to access the NULL primary_channel pointer. System administrators should also consider monitoring for abnormal kernel oops events or VM Bus channel rescind operations that might indicate exploitation attempts. This vulnerability aligns with CWE-476 which specifically addresses NULL pointer dereference issues in software implementations, and could potentially map to ATT&CK technique T1059.003 for privilege escalation if exploited in a virtualized environment where the kernel is accessible to unprivileged users.