CVE-2023-3389 in Linux
Summary
by MITRE • 06/28/2023
A use-after-free vulnerability in the Linux Kernel io_uring subsystem can be exploited to achieve local privilege escalation.
Racing a io_uring cancel poll request with a linked timeout can cause a UAF in a hrtimer.
We recommend upgrading past commit 4716c73b188566865bdd79c3a6709696a224ac04 for 5.10 stable and 0e388fce7aec40992eadee654193cad345d62663 for 5.15 stable.
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Analysis
by VulDB Data Team • 06/28/2023
The vulnerability described in CVE-2023-3389 represents a critical use-after-free condition within the Linux kernel's io_uring subsystem that enables local privilege escalation. This flaw exists in the interaction between io_uring's polling mechanisms and timeout handling, specifically when canceling poll requests that are linked to high-resolution timers. The io_uring subsystem is designed to provide high-performance asynchronous I/O operations for Linux applications, making it a fundamental component in modern kernel architectures. The vulnerability arises from improper synchronization between concurrent operations within the kernel's event handling framework, creating a window where memory objects can be freed while still being referenced by other kernel components.
The technical exploitation of this vulnerability involves a race condition scenario where a malicious local user can simultaneously issue an io_uring cancel poll request and a linked timeout operation. This concurrent execution creates a timing window where the kernel's hrtimer subsystem can be manipulated to trigger a use-after-free condition in the underlying data structures. The flaw is categorized under CWE-416 as a use-after-free vulnerability, which occurs when a program continues to reference memory after it has been freed, leading to unpredictable behavior. The specific implementation issue stems from inadequate reference counting or locking mechanisms within the io_uring subsystem's timeout handling code, where the hrtimer callback function may attempt to access freed memory structures.
The operational impact of this vulnerability is severe as it allows a local attacker with minimal privileges to escalate their access level to root, effectively bypassing kernel security controls. This privilege escalation occurs through the exploitation of kernel memory corruption, which can be leveraged to execute arbitrary code with the highest system privileges. The attack vector is particularly concerning because it requires only local access and does not need network connectivity or specialized hardware. The vulnerability affects multiple kernel versions, specifically targeting the 5.10 and 5.15 stable release branches, making it relevant to a substantial portion of currently deployed Linux systems. This type of vulnerability falls under ATT&CK technique T1068 which involves local privilege escalation through kernel exploits, and T1543 which covers privilege escalation through kernel modules or drivers.
Mitigation strategies for CVE-2023-3389 primarily involve applying the recommended kernel patches that address the race condition in the io_uring subsystem. The fixes provided in commits 4716c73b188566865bdd79c3a6709696a224ac04 for 5.10 stable and 0e388fce7aec40992eadee654193cad345d62663 for 5.15 stable introduce proper synchronization mechanisms and memory management controls. Organizations should prioritize upgrading their kernel versions to patched releases, particularly those running kernel versions 5.10.x and 5.15.x. Additionally, system administrators should implement monitoring for suspicious io_uring usage patterns and consider disabling io_uring functionality if it is not essential for critical applications. The vulnerability demonstrates the importance of proper concurrent programming practices in kernel space, where race conditions can lead to critical security flaws. Regular kernel updates and security audits are essential to prevent exploitation of similar vulnerabilities in the kernel's subsystems, as the io_uring subsystem continues to evolve and gain adoption in modern Linux distributions.