Critical Linux Vulnerability Found to Impact SMB Servers

Dec 27, 2022

A Linux vulnerability with a CVSS score of 10 has been found to affect SMB servers and can lead to remote code execution.

A new flaw has been discovered in the processing of SMB2_TREE_DISCONNECT commands which can lead to remote code execution in servers with ksmbd enabled. KSMBD is an in-kernel SMB file server that was mostly written by a team at Samsung Electronics that was merged into the 5.15 kernel on August 29, 2021. This kernel server implements the SMB3 protocol in kernel space for the sharing of files over a network.

According to the Zero Day Initiative, “The specific flaw exists within the processing of SMB2_TREE_DISCONNECT commands. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the kernel.”

This new vulnerability was discovered back in July 2022 but was only disclosed to the public on December 22, 2022. The good news is twofold: First, the vulnerability has been patched, and second, most are still using SMB and are not affected by this vulnerability. Even so, it’s critical that you apply the patch for kernel 5.15.

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