CVE-2023-1193 in Linux
Summary
by MITRE • 11/01/2023
A use-after-free flaw was found in setup_async_work in the KSMBD implementation of the in-kernel samba server and CIFS in the Linux kernel. This issue could allow an attacker to crash the system by accessing freed work.
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Analysis
by VulDB Data Team • 11/29/2023
The vulnerability identified as CVE-2023-1193 represents a critical use-after-free flaw within the KSMBD implementation of the in-kernel samba server and CIFS subsystem of the Linux kernel. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating a dangerous condition that can be exploited by malicious actors. The flaw specifically resides in the setup_async_work function, which is responsible for managing asynchronous work operations within the kernel's SMB/CIFS implementation. The vulnerability affects the Linux kernel's handling of network file sharing protocols, particularly those implementing the SMB2 and SMB3 protocols through the kernel-space SMBD implementation.
The technical nature of this vulnerability stems from improper memory management within the kernel's SMBD subsystem where the setup_async_work function fails to properly track the lifecycle of allocated memory structures. When an asynchronous work item is created and subsequently freed, the system does not adequately prevent subsequent access to that freed memory location. This creates a window where an attacker can manipulate the execution flow by forcing the system to access the freed memory, potentially leading to arbitrary code execution or system crashes. The vulnerability manifests when network clients connect to a Linux server running the affected kernel version and initiate specific SMB operations that trigger the problematic code path. The use-after-free condition falls under CWE-416, which specifically addresses the use of freed memory in software systems, making it a well-documented and dangerous class of vulnerability.
The operational impact of CVE-2023-1193 is significant as it affects systems running Linux kernels with the KSMBD implementation enabled, particularly those serving SMB/CIFS network shares to client systems. An attacker who successfully exploits this vulnerability could cause system crashes and potentially achieve privilege escalation or arbitrary code execution depending on the attack vector and system configuration. The vulnerability is particularly concerning in enterprise environments where Linux servers often serve as file shares for multiple users and applications, as it could be leveraged to disrupt services or gain unauthorized access to sensitive data. The impact extends beyond simple service disruption to potential data compromise, as the system could be manipulated to execute malicious code with kernel-level privileges. This vulnerability directly aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, making it a serious concern for system administrators and security professionals.
Mitigation strategies for CVE-2023-1193 primarily involve applying the latest kernel updates from the Linux kernel maintainers, as patches have been developed to address the memory management issue in the setup_async_work function. System administrators should prioritize patching affected systems, particularly those serving SMB/CIFS shares to external networks. Network segmentation and access controls should be implemented to limit exposure to the vulnerable service, while monitoring systems should be configured to detect unusual network activity that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management practices in kernel space code and emphasizes the need for rigorous code review processes to identify similar use-after-free conditions. Organizations should also consider implementing intrusion detection systems that can monitor for known exploitation patterns and maintain regular security assessments of their kernel implementations. The fix typically involves ensuring that freed memory structures are properly invalidated and that subsequent access attempts are properly handled to prevent the use-after-free condition from being exploited.