CVE-2023-32247 in Linux
Summary
by MITRE • 07/24/2023
A flaw was found in the Linux kernel's ksmbd, a high-performance in-kernel SMB server. The specific flaw exists within the handling of SMB2_SESSION_SETUP commands. The issue results from the lack of control of resource consumption. An attacker can leverage this vulnerability to create a denial-of-service condition on the system.
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Analysis
by VulDB Data Team • 08/27/2024
The vulnerability identified as CVE-2023-32247 resides within the Linux kernel's ksmbd implementation, which serves as a high-performance in-kernel Server Message Block protocol server. This flaw specifically manifests during the processing of SMB2_SESSION_SETUP commands, representing a critical weakness in the kernel's network protocol handling capabilities. The ksmbd subsystem is designed to provide SMB/CIFS file sharing functionality directly within the kernel space, offering improved performance over user-space implementations while maintaining compatibility with Microsoft's SMB protocols. The vulnerability stems from insufficient resource management controls during session establishment phases, creating an exploitable condition that can be leveraged by malicious actors to disrupt system operations.
The technical root cause of this vulnerability lies in the improper handling of resource consumption during SMB2_SESSION_SETUP command processing. When a client attempts to establish an SMB session through the ksmbd server, the kernel fails to adequately monitor or limit the resources consumed during this critical phase of authentication and connection establishment. This lack of resource control allows an attacker to submit specially crafted session setup requests that consume excessive system resources without proper bounds checking or resource limiting mechanisms. The flaw essentially creates a resource exhaustion scenario where malicious requests can continuously consume memory, CPU cycles, or other system resources, leading to system instability and operational degradation.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it can effectively render the targeted system unavailable to legitimate users while potentially causing system crashes or severe performance degradation. When exploited, the vulnerability allows an attacker to consume system resources at an unsustainable rate, leading to memory exhaustion, CPU starvation, or other resource contention issues that can affect the entire system's ability to function properly. This makes the vulnerability particularly dangerous in environments where SMB services are actively used, such as file servers, network-attached storage systems, or any infrastructure relying on ksmbd for file sharing capabilities. The impact is amplified in high-traffic environments where legitimate users may be unable to access shared resources due to the resource exhaustion caused by the malicious session setup attempts.
Mitigation strategies for CVE-2023-32247 should focus on implementing proper resource limiting and monitoring mechanisms within the ksmbd subsystem. System administrators should consider applying kernel updates that contain patches addressing this specific resource consumption flaw, as these patches typically implement proper bounds checking and resource management controls during session setup operations. Additionally, network-level controls such as rate limiting, connection throttling, and access control lists can help reduce the impact of potential exploitation attempts. The vulnerability aligns with CWE-770, which addresses excessive resource consumption, and represents a classic example of resource exhaustion attacks that can be mitigated through proper resource management and monitoring practices. Organizations should also consider implementing intrusion detection systems that can identify unusual session setup patterns and alert administrators to potential exploitation attempts, as this vulnerability can be detected through abnormal resource consumption patterns that deviate from normal operational baselines.