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CVE-2026-74497
ALSA: usb-audio: Clamp frame size in implicit-feedback mode
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem sound/usb. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74497 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
snd_usb_handle_sync_urb() scales received sync packet sizes by the sender's stride and stores the result directly in out_packet->packet_size[i]. If a connected USB device sends an oversized sync packet, this frame count can exceed ep->maxframesize. The un-clamped frame count then propagates to the playback endpoint queue, potentially driving packet transfers beyond the endpoint's hardware frame limits. Cap the calculated frame count against ep->maxframesize in snd_usb_handle_sync_urb() to prevent oversized packets from entering the playback queue.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
sound/usb/endpoint.c
- What this is
- SOUNDMAINTAINERS section matched on sound/ · linux-sound@vger.kernel.org · Maintained
- Kernel module
- snd_usb_audio
Check it on the machine
grep -wE 'CONFIG_SND|CONFIG_SND_USB_AUDIO' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w snd_usb_audioPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_SND, CONFIG_SND_USB_AUDIO
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 3.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- sound/usb
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.8 | 5.10.265 | 2d39fea6d3c1 |
| 3.8 | 5.15.216 | 09cf3dbbb425 |
| 3.8 | 6.1.183 | cfa8d3e0e8b8 |
| 3.8 | 6.6.151 | 56ac3e7c90f6 |
| 3.8 | 6.12.103 | be97fea7451d |
| 3.8 | 6.18.44 | 2db4535d6af7 |
| 3.8 | 7.1.8 | 53f0aa37eb94 |
| 3.8 | 7.2 | 8d7a30c50c2e |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached via local ALSA USB-audio PCM syscalls (open/hw_params/prepare/trigger) that start isochronous streaming; once implicit-feedback playback is active, malicious inbound USB sync URB completions invoke snd_usb_handle_sync_urb() without any network path.
- AC:LAttack complexity, low
- A malicious USB audio gadget can deterministically send oversized implicit-feedback sync isochronous packets during active playback; the attacker controls both the device firmware and timing, with no race or uncontrollable memory-layout dependency required.
- PR:NPrivileges required, none
- Exploitation is driven by a connected malicious USB audio device sending crafted isochronous IN packets; the attacker needs no host account, kernel capability, or user-namespace privilege on the victim system once playback is running.
- UI:NUser interaction, none
- After implicit-feedback USB audio playback is started, the malicious device can continuously inject oversized sync packets without further victim interaction; no additional discretionary user actions are needed beyond normal streaming operation.
- S:UScope, unchanged
- Impact is confined to host-kernel USB-audio transfer-buffer corruption and crashes within the same kernel security authority; it does not constitute a VM escape, IOMMU bypass, or other cross-scope boundary violation.
- C:HConfidentiality impact, high
- Uncapped frame counts stored in the playback queue propagate into URB preparation, causing out-of-bounds access against kernel-coherent USB DMA transfer buffers and adjacent heap memory, enabling information disclosure from corrupted kernel memory.
- I:HIntegrity impact, high
- Oversized packet_size values drive memset/copy and iso_frame_desc lengths beyond allocated URB buffer bounds in prepare_silent_urb() and prepare_playback_urb(), yielding controllable out-of-bounds kernel memory writes and heap corruption.
- A:HAvailability impact, high
- The resulting kernel memory corruption and invalid oversized URB transfers trigger kernel oops/panic and repeatable audio-pipeline failure; related mitigations for this implicit-feedback packet-size mismatch explicitly document crash behavior from the same root cause.