CVE-2023-52441 - Linux Kernel Vulnerability Patched in ksmbd: Fix Out-of-bounds Issue in init_smb2_rsp_hdr()

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In a recent update to the Linux kernel, an important vulnerability has been patched which pertains to the "ksmbd" module. This vulnerability, designated as CVE-2023-52441, occurs due to an out-of-bounds issue when the function 'init_smb2_rsp_hdr()' is called. This can lead to unexpected behavior and potential security risks if a client sends an SMB2 negotiate request following an SMB1 negotiate request.

The patch applied fixes this problem by ignoring SMB1 packets after the 'need_neg' flag is set to false. The original references for this vulnerability can be found on the CVE website here.

Code Snippet

Here is a sample code snippet that demonstrates the key parts of the patch applied to the Linux kernel to address this vulnerability:

static int ksmbd_decode_smb1_pdu(struct ksmbd_work *work)
{
    /* ... */

    // Check if the need_neg flag is false and the header is an SMB1 negotiate request
    if (!work->conn->need_neg && header->Command == SMB_COM_NEGOTIATE)
    {
            ksmbd_debug(SMB, "Ignore SMB1 packets after ->need_neg is set to false\n");
            return -EINVAL;
    }

    /* ... */
}

In this code snippet, the function ksmbd_decode_smb1_pdu() checks if the need_neg flag has been set to false and if the incoming header is an SMB1 negotiate request. If both conditions are met, it will log a debug message and return an error value.

Exploit Details

Before the patch was applied, if a client sent an SMB2 negotiate request followed by an SMB1 negotiate request, the function init_smb2_rsp_hdr() would be called for the SMB1 negotiate request since the need_neg flag had been set to false. This could then lead to incorrect processing and handling of packets as the two types of negotiate requests should be treated differently.

This vulnerability highlights the importance of ensuring that code handling complex protocols, such as SMB, is well-structured and properly handles all possible edge cases. By patching this vulnerability, Linux systems using the ksmbd module can be more secure against potential attacks utilizing this issue.

Conclusion

CVE-2023-52441 is a Linux kernel vulnerability that could have introduced security risks for systems using the ksmbd module, due to an out-of-bounds issue in the init_smb2_rsp_hdr() function. Thankfully, the vulnerability has been patched in recent kernel updates, making systems more robust against such attack vectors.

It is always essential for system administrators to keep their kernel up to date, as any outdated software can be exploited by malicious parties. Stay vigilant and secure by regularly monitoring the latest patch releases and applying them to your systems.

For more information on this particular patch, you can refer to the original references available on the CVE website here.

Timeline

Published on: 02/21/2024 08:15:45 UTC
Last modified on: 03/15/2024 13:56:31 UTC