high CVSS 7.8 Actively exploited

CVE-2024-53197·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices A bogus device can provide a bNumConfigurations value that exceeds the initial value used in usb_get_configuration for allocating dev->config. This can lead to out-of-bounds accesses later, e.g. in usb_destroy_configuration.

Severity
high
Software
Kernel
Fixed in
6.12.2
Published
2024-12-27

Affected versions

From: 6.12

Until: 6.12.2

Fixed in: 6.12.2

How to fix this CVE

Update the Linux kernel to a patched version. If USB audio devices are not used on the server, blacklist the snd-usb-audio module. Restrict physical USB access and use USBGuard to whitelist authorized devices.

sudo apt update && sudo apt install --only-upgrade linux-image-generic
sudo reboot
# Disable USB audio if not needed:
echo 'blacklist snd-usb-audio' | sudo tee /etc/modprobe.d/blacklist-usb-audio.conf
sudo update-initramfs -u

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

Physical access attack via malicious USB audio device. The attacker connects a crafted USB device identifying as an Extigy or Mbox audio interface with a bogus bNumConfigurations value. The kernel's USB audio driver trusts this value for array indexing, causing an out-of-bounds read/write in the configuration parsing code.

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

WAF cannot mitigate physical USB attacks. Compensating controls:
- Blacklist snd-usb-audio on servers that do not need USB audio
- Deploy USBGuard with a whitelist policy
- Disable USB ports in BIOS/UEFI on headless servers
- Restrict physical access to server hardware
- Enable kernel lockdown mode where supported

How to check if you are affected

  1. Check if snd-usb-audio module is loaded: lsmod | grep snd_usb_audio
  2. Check kernel version against distribution security advisories
  3. Monitor USB device events: dmesg | grep -i 'usb.*audio\|extigy\|mbox'
  4. Check for USBGuard: systemctl status usbguard
  5. List connected USB devices: lsusb -v 2>/dev/null | grep -B5 -A5 'Audio'
  6. Verify USB authorization policy: cat /sys/bus/usb/devices/*/authorized

Indicators of compromise

  • USB audio devices appearing with unusual bNumConfigurations values in dmesg
  • Kernel oops or KASAN reports in snd-usb-audio or usb_audio_probe
  • Unexpected snd-usb-audio module loads on headless servers
  • Physical access events correlated with kernel crashes

FAQ

Are headless servers at risk?

Only if an attacker can physically connect a USB device. Headless servers in locked data centers have minimal risk. However, servers with USB ports exposed (colocation, edge deployments) or USB-over-IP setups could be targeted.

Can this be exploited remotely?

No. Physical USB access is required to connect the malicious device. Remote exploitation is not possible unless USB-over-IP or similar technology exposes USB ports to the network.

Does this affect virtual machines?

Only if USB passthrough is configured from host to guest. Standard virtualized environments without USB device passthrough are not affected.

Why are Extigy and Mbox specifically mentioned?

The vulnerable code has special handling for these specific USB audio devices (SB Extigy and Digidesign Mbox). The special parsing code for these devices does not validate the bNumConfigurations field, while generic USB audio device handling is not affected.

Should I blacklist snd-usb-audio on all servers?

Yes, for servers that do not use USB audio devices. This eliminates the entire attack surface. Almost no server workload requires USB audio.

Related Kernel CVEs

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CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.
CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
CVE-2021-47548CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port() The if statement: if (port >= DSAF_GE_NUM) return; limits the value of port less than DSAF_GE_NUM (i.e., 8). However, if the value of port is 6 or 7, an array overflow could occur: port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off; because the length of dsaf_dev->mac_cb is DSAF_MAX_PORT_NUM (i.e., 6). To fix this possible array overflow, we first check port and if it is greater than or equal to DSAF_MAX_PORT_NUM, the function returns.

References

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