CVE-2024-43883 in Linux
Summary
by MITRE • 08/23/2024
In the Linux kernel, the following vulnerability has been resolved:
usb: vhci-hcd: Do not drop references before new references are gained
At a few places the driver carries stale pointers to references that can still be used. Make sure that does not happen. This strictly speaking closes ZDI-CAN-22273, though there may be similar races in the driver.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/09/2025
The vulnerability identified as CVE-2024-43883 resides within the Linux kernel's usb vhci-hcd driver, which manages virtual host controller interface devices for USB communication. This particular flaw represents a classic race condition scenario where the driver improperly handles reference counting mechanisms during concurrent operations. The vulnerability stems from the driver's failure to maintain proper reference lifecycle management, creating conditions where stale pointers may persist in memory while new references are being established. Such issues commonly arise in kernel space drivers where multiple threads or processes may simultaneously access and modify shared data structures without adequate synchronization mechanisms. The problematic behavior manifests when the driver drops references to objects before acquiring new references, potentially leaving dangling pointers that could be dereferenced later, leading to unpredictable system behavior or potential privilege escalation.
The technical implementation of this vulnerability involves improper reference counting within the vhci-hcd driver's handling of USB device connections and disconnections. When the driver processes USB operations, it maintains internal reference counters to track the usage of various data structures and objects. The flaw occurs during transitions where the driver releases references to certain objects before establishing new references to the same or related objects. This creates a temporal window where other system components might still hold valid references to the now-released objects, resulting in what is known as a use-after-free condition or more specifically a stale pointer dereference. The vulnerability's classification aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, and potentially CWE-416, concerning the use of freed memory. The underlying issue demonstrates poor resource management practices where the driver fails to properly sequence reference operations, allowing for inconsistent state management during concurrent USB operations.
The operational impact of CVE-2024-43883 extends beyond simple system instability, potentially enabling privilege escalation or denial of service conditions within the kernel space. When stale pointers are dereferenced, the system may access memory locations that have been reallocated for other purposes, leading to arbitrary code execution or system crashes. This vulnerability affects systems running Linux kernels that utilize the vhci-hcd driver for USB virtualization, particularly those supporting virtualized USB environments or USB device passthrough functionality. The risk is heightened in server environments or embedded systems where USB virtualization is commonly employed for device management or debugging purposes. Attackers could potentially exploit this race condition to gain elevated privileges within the kernel, as the improper reference handling may allow manipulation of kernel data structures or memory layouts. The vulnerability's potential for exploitation aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel exploits, and T1547, covering registry run keys and startup folder modifications that could occur as a result of successful exploitation.
Mitigation strategies for CVE-2024-43883 focus primarily on applying the official kernel patch that resolves the reference counting race condition within the vhci-hcd driver. System administrators should immediately update their Linux kernel installations to versions containing the fix, which typically involves proper sequencing of reference acquisition and release operations. The patch ensures that references are only dropped after new references have been successfully acquired, eliminating the temporal window where stale pointers could exist. Organizations should implement comprehensive kernel update policies and conduct regular security assessments to identify systems running vulnerable kernel versions. Additional mitigations include monitoring for unusual system behavior or kernel crashes that might indicate exploitation attempts, and implementing proper USB device access controls to limit exposure. The fix also incorporates defensive programming practices such as proper locking mechanisms and atomic operations to prevent concurrent access violations. Security teams should also consider deploying kernel-based security modules or extended protection mechanisms that can detect and prevent exploitation attempts targeting similar race conditions in other kernel subsystems.