The Linux kernel is an essential part of the open-source Linux operating system, which serves as an interface between the computer's hardware and its software applications. Consequently, it is crucial to ensure its security to keep the system protected from potential threats. In this post, we will explore the recent vulnerability CVE-2024-56590 found in the Linux kernel, describe its exploit details, and provide the necessary fixes to resolve the issue.

CVE-2024-56590 Vulnerability Overview

The vulnerability CVE-2024-56590 specifically involves the Bluetooth subsystem of the Linux kernel, known as hci_core. The Bluetooth subsystem is responsible for managing and controlling Bluetooth devices connected to the system. The flaw involves not checking the proper skb (socket buffer) length when processing the hci_acldata_packet. If the skb does not contain the correct ACL (Access Control List) header, the code might accidentally access uninitialized or invalid memory, leading to potential issues such as data corruption or even a system crash.

Exploit Details

The exploit triggered by this vulnerability can lead to a Denial of Service (DoS) attack, unauthorized data disclosure, or even arbitrary code execution if the attacker can manipulate the ACL header in the skb buffer. In the worst-case scenario, this vulnerability can be exploited by malicious hackers to gain unauthorized access to a victim's system and execute arbitrary code, potentially compromising the security and privacy of the user's data.

The issue in the Linux kernel Bluetooth subsystem can be found in the following code

void hci_acldata_packet(struct hci_dev *hdev, struct sk_buff *skb) {
    struct hci_acl_hdr *ah;
    // ...

    ah = (void *) skb->data; // This line doesn't check if skb really contains an ACL header
    // ...
}

To mitigate the security risk, we need to make sure the skb buffer contains a valid ACL header before accessing it implicitly. The updated version of the hci_acldata_packet function would include a check for the skb length as follows:

void hci_acldata_packet(struct hci_dev *hdev, struct sk_buff *skb) {
    struct hci_acl_hdr *ah;
    // ...

    if (skb->len < sizeof(*ah))
        return;

    ah = (void *) skb->data; // Now the code only proceeds if skb contains a valid ACL header
    // ...
}

Original References

1. The bug report outlining the vulnerability can be found on the Linux Kernel Mailing List's website: https://lkml.org/lkml/2024/2/24/91
2. The official patch that resolves the issue in the Linux kernel can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=038c9576f288

Conclusion

The CVE-2024-56590 vulnerability in the Linux kernel could have harmful consequences for users if exploited by malicious hackers. However, with the appropriate fix in place, including the check for skb length before accessing the ACL header, users can rest assured that their data will remain secure. As always, it is crucial to keep your Linux system updated to the latest kernel version to protect it from potential security flaws such as the CVE-2024-56590 vulnerability.

Timeline

Published on: 12/27/2024 15:15:18 UTC
Last modified on: 01/20/2025 06:23:41 UTC