high CVSS 7.8 Actively exploited EPSS 1.8%

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

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 1.8% — higher than 83% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

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-2026-53399CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nfsd: release layout stid on setlease failure nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer. The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail. A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work. nfsd4_alloc_layout_stateid() nfs4_alloc_stid() /* idr_alloc_cyclic under cl_lock */ nfsd4_layout_setlease() /* fails */ nfs4_put_stid() nfsd4_free_layout_stateid() delayed_work_pending(&ls->ls_fence_work) /* needs INIT */ nfsd4_close_layout() /* nfsd_file_put(ls->ls_file) */ put_nfs4_file() Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).

References

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