CVE-2023-40283: Linux Kernel L2CAP Socket Use-After-Free Vulnerability Analysis and Exploitation

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Introduction

A newly discovered vulnerability (CVE-2023-40283) exists in the Linux kernel in the file net/bluetooth/l2cap_sock.c that may allow attackers to exploit a Use-After-Free condition. This article will provide an in-depth analysis of the vulnerability, affected versions, code snippets, links to original references, and exploit details.

Vulnerability Details

The issue is present in the Linux kernel's Bluetooth L2CAP subsystem, specifically in the l2cap_sock_release function. This function is responsible for releasing an L2CAP socket when it is no longer needed by a user process.

The vulnerability results from mishandling the children of a socket object (sk) that has already been freed. This Use-After-Free condition occurs because the kernel fails to properly track the references to an allocated L2CAP socket in certain cases.

Affected Versions

The vulnerability affects Linux kernel versions before 6.4.10.

Below is a simplified snippet of the l2cap_sock_release function from net/bluetooth/l2cap_sock.c

void l2cap_sock_release(struct socket *sock)
{
    struct sock *sk = sock->sk;

    if (!sk)
        return;

    BT_DBG("sk %p", sk);

    /* Other code */

    sock_orphan(sk);

    /* Here is the issue: children of sk are mishandled */
    while ((sk = bt_sock_dequeue(&hdev->l2cap_sock_list, sk)) != NULL) {
        /* Exploit can occur due to Use-After-Free condition */
    }

    /* Other code */

    sock_put(sk);
}

The code fails to properly manage the children of the sk object, introducing a Use-After-Free condition.

Original References

1. Official Linux kernel Git repository: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
2. Official Linux kernel source code: net/bluetooth/l2cap_sock.c
3. Official CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40283
4. Official Linux kernel mailing list discussion: https://lore.kernel.org/netdev/patch/

Exploit Details

An attacker can potentially exploit this vulnerability by creating multiple children for a socket object (sk) and then releasing the parent socket. By doing so, the attacker can trigger the Use-After-Free condition and cause undefined behavior in the kernel, which may lead to a crash, corruption of kernel data structures, or remote code execution.

Conclusion

In summary, CVE-2023-40283 is a dangerous Linux kernel vulnerability that affects the Bluetooth L2CAP subsystem. By exploiting this vulnerability, an attacker could potentially compromise the integrity and confidentiality of a victim's system. It is vital for users to ensure they are using a Linux kernel version 6.4.10 or later and adhere to the best security practices, such as regularly patching their systems.

Timeline

Published on: 08/14/2023 03:15:00 UTC
Last modified on: 10/11/2023 19:15:00 UTC