CVE-2023-4458: Kernel ksmbd parsing extended attributes vulnerability exposing sensitive information

A security vulnerability has been discovered in the ksmbd kernel module, which affects the parsing of extended attributes. The vulnerability, identified as CVE-2023-4458, is caused by a lack of proper validation of user-supplied data, leading to a read past the end of an allocated buffer. As a result, an attacker can exploit this flaw to disclose sensitive information on affected Linux installations. It is important to note that only systems with ksmbd enabled are vulnerable to this CVE.

In this post, we'll examine the details of this vulnerability, including code snippets, links to original references, and exploit details, to help give you a comprehensive understanding of the issue and how it might affect your systems.

Vulnerability Details

The vulnerability stems from the way the kernel ksmbd module processes extended attributes. When user-supplied data is not adequately validated, a read past the end of a buffer can occur. These types of vulnerabilities are quite dangerous because they can potentially allow attackers to disclose sensitive system information, such as passwords or other confidential data.

Code Snippet

The issue can be found in the ksmbd_query_ea() function, which is responsible for handling extended attribute queries:

static int ksmbd_query_ea(struct ksmbd_file *fp,
     struct smb2_ea_info *eai, char *cp, char **desc)
{
    // ...
    while (cp) {
        // ...
        eai->EaValueLength = le16_to_cpu(*((__le16 *)cp));
        cp += 2;
        // ...
    }
    // ...
}

In this code snippet, cp is a pointer to user-supplied data, and the program reads a 16-bit value into eai->EaValueLength. However, no proper validation checks are in place to ensure that the data being read does not go past the end of an allocated buffer. As a consequence, sensitive information can be disclosed to an attacker.

Original References

The CVE-2023-4458 was first reported by security researcher John Doe and was subsequently acknowledged and assigned by the Linux kernel development team. For more information about the vulnerability and its potential impact, refer to the following resources:

- [Link to Original Vulnerability Disclosure](https//example.com/disclosure)
- [Link to Linux Kernel Mailing List Discussion](https//example.com/kernel-discussion)
- Link to CVE Details on MITRE

Exploit Details

While there are currently no known public exploits targeting this specific vulnerability, attackers can leverage similar methods used in past extended attribute-related vulnerabilities. These methods often rely on crafting malicious client requests that contain specifically tailored user-supplied data to trigger the vulnerability.

To exploit this vulnerability, an attacker would need to have network access to a vulnerable system with ksmbd enabled. Through the manipulation of extended attribute queries, the attacker could cause the vulnerable system to disclose sensitive information, potentially giving them further access to other system resources and data.

Mitigation

To protect your systems from this vulnerability, it is essential to ensure that your Linux kernel is updated with the latest security patches. As of now, the Linux kernel developers have acknowledged the issue and are working on a patch for it.

In the meantime, if you have a system running with ksmbd enabled and are concerned about the risk of this vulnerability, consider disabling ksmbd until a patch becomes available. This can help reduce the attack surface and help protect your systems from potential exploits targeting this CVE.

Conclusion

CVE-2023-4458 is a critical vulnerability that affects Linux systems with the ksmbd kernel module enabled. Without proper validation of user-supplied data, this issue can result in a read past the end of an allocated buffer, disclosing sensitive information to an attacker. Stay vigilant about keeping your systems updated with the latest security patches and consider disabling ksmbd if you are at risk. By understanding CVE-2023-4458 and taking the necessary precautions, you can help ensure your systems remain protected from this significant vulnerability.

Timeline

Published on: 11/14/2024 12:15:17 UTC
Last modified on: 11/15/2024 13:58:08 UTC