CVE-2023-0240 in Linux
Summary
by MITRE • 01/30/2023
There is a logic error in io_uring's implementation which can be used to trigger a use-after-free vulnerability leading to privilege escalation. In the io_prep_async_work function the assumption that the last io_grab_identity call cannot return false is not true, and in this case the function will use the init_cred or the previous linked requests identity to do operations instead of using the current identity. This can lead to reference counting issues causing use-after-free. We recommend upgrading past version 5.10.161.
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Analysis
by VulDB Data Team • 07/29/2026
The vulnerability identified as CVE-2023-0240 represents a critical logic error within the io_uring subsystem of the Linux kernel that fundamentally compromises system security through privilege escalation. This flaw exists in the io_prep_async_work function where the kernel's implementation makes an incorrect assumption about the io_grab_identity call behavior. The vulnerability manifests when the io_grab_identity function returns false, which contradicts the developers' assumptions and creates a dangerous execution path. This logic error creates a use-after-free condition that can be exploited by malicious actors to gain elevated privileges within the system.
The technical flaw stems from improper reference counting and identity management within the io_uring asynchronous I/O framework. When io_grab_identity fails to return true, the function continues execution using either init_cred or a previous linked request's identity instead of the current identity context. This mismanagement of credential references creates a scenario where memory objects that should have been freed are still being accessed, leading to use-after-free conditions. The vulnerability specifically affects the kernel's handling of asynchronous work requests and demonstrates a failure in proper resource lifecycle management that violates fundamental security principles. The flaw is categorized under CWE-415 as an improper handling of memory allocation and deallocation, with the potential for privilege escalation through improper credential handling.
The operational impact of CVE-2023-0240 is severe and potentially catastrophic for systems running affected kernel versions. An attacker with local access can exploit this vulnerability to escalate privileges from unprivileged user accounts to root level access, effectively bypassing all system security controls. The use-after-free condition creates a stable exploitation vector that can be leveraged for persistent system compromise, allowing attackers to execute arbitrary code with the highest system privileges. This vulnerability affects systems using kernel versions prior to 5.10.161, making it particularly concerning for organizations that have not yet applied the necessary security patches. The exploitation of this flaw can lead to complete system compromise, data exfiltration, and establishment of persistent backdoors within the affected infrastructure.
Mitigation strategies for CVE-2023-0240 center exclusively on upgrading to kernel versions 5.10.161 or later where the logic error has been corrected. Organizations should implement immediate patch management procedures to ensure all systems are updated with the latest kernel security patches. Additionally, monitoring systems should be configured to detect any suspicious privilege escalation attempts that might indicate exploitation attempts. The vulnerability's presence in the io_uring subsystem means that any applications or services relying on asynchronous I/O operations may be at risk, necessitating comprehensive system auditing. Security teams should also consider implementing runtime protections and monitoring for abnormal credential usage patterns that could indicate exploitation attempts. According to ATT&CK framework, this vulnerability maps to privilege escalation techniques under T1068, and the exploitation could potentially lead to lateral movement and persistence through the T1074 and T1078 techniques, making comprehensive network monitoring essential for detection.