CVE-2023-53006 in Linux
Summary
by MITRE • 03/27/2025
In the Linux kernel, the following vulnerability has been resolved:
cifs: Fix oops due to uncleared server->smbd_conn in reconnect
In smbd_destroy(), clear the server->smbd_conn pointer after freeing the smbd_connection struct that it points to so that reconnection doesn't get confused.
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2023-53006 represents a critical memory management flaw within the Linux kernel's CIFS (Common Internet File System) implementation that could lead to system instability and potential denial of service conditions. This issue specifically affects the SMBD (Server Message Block Direct) connection handling mechanism used for high-performance file sharing operations. The vulnerability stems from improper pointer cleanup during the reconnection process, creating a scenario where stale references can persist in memory and cause unexpected behavior when the system attempts to establish new connections.
The technical root cause of this vulnerability lies in the smbd_destroy() function which manages the cleanup of SMBD connection structures. When the kernel processes a reconnection event, it fails to properly clear the server->smbd_conn pointer after freeing the underlying smbd_connection structure that this pointer references. This creates a dangling pointer condition where the system maintains a reference to memory that has already been deallocated, leading to potential memory corruption and system crashes. The flaw manifests as an oops condition, which is the Linux kernel's way of reporting a critical error that typically results in system instability and requires manual intervention to recover.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the availability of file sharing services and create denial of service conditions for legitimate users. When the CIFS subsystem attempts to reconnect to a server after a network disruption or other connection issues, the stale pointer reference causes unpredictable behavior in the kernel's memory management system. This can result in the kernel entering an inconsistent state where subsequent connection attempts fail or cause the system to panic and reboot. The vulnerability particularly affects systems heavily reliant on CIFS file sharing, including enterprise environments with extensive network file server deployments, where connection stability is critical for business operations.
Security researchers have classified this vulnerability as a memory safety issue that aligns with CWE-415, which addresses double free errors and improper cleanup of memory resources. The flaw demonstrates poor resource management practices within the kernel's SMBD implementation, where the cleanup sequence does not properly maintain pointer integrity. From an attack perspective, while this vulnerability may not directly enable remote code execution, it creates a reliable vector for denial of service attacks that can disrupt file sharing services and potentially be used as a component in broader attack strategies. The ATT&CK framework categorizes this as a system compromise technique through resource exhaustion and memory corruption, as it targets fundamental kernel memory management functions that are essential for system stability. Organizations should prioritize patching this vulnerability through kernel updates, as the fix involves a straightforward but critical change to ensure proper pointer clearing in the smbd_destroy() function. The resolution addresses the core issue by explicitly clearing the server->smbd_conn pointer after freeing the associated memory structure, preventing the dangling pointer condition that leads to system oops and potential crashes during reconnection scenarios.