CVE-2022-4744 in Linux
Summary
by MITRE • 03/31/2023
A double-free flaw was found in the Linux kernel’s TUN/TAP device driver functionality in how a user registers the device when the register_netdevice function fails (NETDEV_REGISTER notifier). This flaw allows a local user to crash or potentially escalate their privileges on the system.
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Analysis
by VulDB Data Team • 10/17/2025
The vulnerability identified as CVE-2022-4744 represents a critical double-free flaw within the Linux kernel's TUN/TAP device driver implementation. This issue manifests in the specific context of how the kernel handles device registration when the register_netdevice function encounters failure through the NETDEV_REGISTER notifier mechanism. The TUN/TAP virtual network interfaces are commonly used for creating virtual network devices that allow userspace applications to send and receive network packets directly, making them integral components in various networking scenarios including virtualization platforms, VPN implementations, and network monitoring tools. The flaw exists in the kernel's memory management logic during the device registration process, where improper handling of memory allocation and deallocation sequences creates opportunities for malicious exploitation.
The technical exploitation of this vulnerability stems from the kernel's failure to properly manage memory references when device registration fails. When the register_netdevice function returns an error condition through the NETDEV_REGISTER notifier, the kernel's TUN/TAP driver implementation attempts to free memory resources that may have already been freed or are in an inconsistent state. This double-free condition occurs because the driver logic does not adequately track the memory allocation status or properly handle the cleanup sequence when registration fails. The flaw specifically impacts the kernel's memory management subsystem where the same memory block gets deallocated twice, potentially leading to memory corruption that can be leveraged by local attackers. This type of vulnerability falls under the Common Weakness Enumeration category CWE-415, which specifically addresses double free conditions in memory management operations.
The operational impact of CVE-2022-4744 extends beyond simple system crashes to include potential privilege escalation capabilities that make it particularly dangerous for local attackers. A local user with access to the system can exploit this vulnerability to cause system instability through kernel crashes or more severely by manipulating the memory corruption to execute arbitrary code with kernel privileges. The nature of TUN/TAP interfaces means that many legitimate applications and services rely on these virtual devices, making the attack surface broader than initially apparent. The vulnerability is particularly concerning in environments where multiple users share systems or where untrusted applications have access to TUN/TAP device creation capabilities. This flaw can be exploited to gain root privileges, effectively compromising the entire system security posture and potentially allowing attackers to establish persistent backdoors or exfiltrate sensitive data.
Mitigation strategies for CVE-2022-4744 should focus on both immediate patching and operational security measures. The primary solution involves applying the kernel patches released by the Linux kernel team that address the improper memory management logic in the TUN/TAP driver's error handling code. Organizations should prioritize updating their systems to the patched kernel versions as soon as possible, particularly in environments where local privilege escalation risks are unacceptable. Additional operational mitigations include restricting access to TUN/TAP device creation capabilities through proper access controls and user privilege management, implementing monitoring for suspicious network device creation activities, and conducting regular security audits of systems that utilize virtual network interfaces. The vulnerability demonstrates the importance of proper error handling in kernel space and highlights the need for comprehensive testing of failure scenarios in device driver implementations. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through kernel exploits and system compromise via local access, making it a critical target for both defensive and offensive security operations.