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CVE-2026-74641
ALSA: usx2y: bound the hwdep mmap fault offset
Published 2026-08-22 (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-2026-74641 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 | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. 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_us428ctls_vm_fault() turns the faulting page offset into a kernel address with no bound of any kind: offset = vmf->pgoff << PAGE_SHIFT; vaddr = (char *)(...)->us428ctls_sharedmem + offset; page = virt_to_page(vaddr); get_page(page); vmf->page = page; return 0; snd_us428ctls_mmap() checks only the length of the mapping, never the offset, and us428ctls_sharedmem is a single page from alloc_pages_exact(). For a character device file_mmap_size_max() returns ULONG_MAX, so the mm layer imposes no ceiling either. Every page offset above zero resolves to a struct page outside the object, and the handler installs it into the caller's address space read-write; the vma is not marked read-only. The caller picks the page frame with a single mmap() argument and gets read-write access to a page of kernel memory it does not own; an offset that lands in an unpopulated vmemmap region oopses instead. A process that can open the hwdep node of an attached US-X2Y reaches this after loading the FPGA image through the same node; no capability check is involved. On 7.2.0-rc5 (arm64), mmap() with a large offset: Unable to handle kernel paging request at virtual address fffffdffc45d5ac8 pc : snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y] Call trace: snd_us428ctls_vm_fault+0x68/0x140 [snd_usb_usx2y] __do_fault __handle_mm_fault handle_mm_fault el0_da Reject any offset outside the shared region. The pcm hwdep handler in usx2yhwdeppcm.c computes its address the same way and needs the same bound. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>
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/usx2y/usX2Yhwdep.c
sound/usb/usx2y/usx2yhwdeppcm.c
- What this is
- SOUNDMAINTAINERS section matched on sound/ · linux-sound@vger.kernel.org · Maintained
- Kernel module
- snd_usb_usx2y
Check it on the machine
grep -wE 'CONFIG_SND|CONFIG_SND_USB_USX2Y' /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_usx2yPrints 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.
- bookwormMnot built on amd64/cloud-amd64, arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- trixieMnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_SND, CONFIG_SND_USB_USX2Y
- 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
- 2026-08-22 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.3% 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 |
|---|---|---|
| 2.6.12 | 5.10.266 | ad6fedea65c6 |
| 2.6.12 | 5.15.216 | 10a87401fb31 |
| 2.6.12 | 6.1.183 | 34ab56ed854b |
| 2.6.12 | 6.6.152 | 4208db2453e1 |
| 2.6.12 | 6.12.104 | f613b4a2d872 |
| 2.6.12 | 6.18.45 | f75d6f61f0d9 |
| 2.6.12 | 7.1.9 | 5bf5ccddf00b |
| 2.6.12 | 7.2 | 2ca1eea3cd17 |
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
- Exploitation requires local mmap() on the ALSA hwdep character device (/dev/snd/hwC*D*); the path is open→SNDRV_HWDEP_IOCTL_DSP_LOAD→mmap→snd_us428ctls_vm_fault, with no network or remote packet handler involved.
- AC:LAttack complexity, low
- The attacker fully controls the mmap() page offset (vmf->pgoff); any offset beyond the single-page shared buffer deterministically maps an attacker-chosen kernel page read-write or oopses, with no race or uncontrollable memory-layout dependency.
- PR:LPrivileges required, low
- The driver performs no capability checks on hwdep open, ioctl, or mmap; any unprivileged local user who can access the hwdep node (typically via the audio group on desktop distros) can reach the fault handler after loading the FPGA image.
- UI:NUser interaction, none
- All exploitation steps—opening the hwdep node, loading FPGA firmware via DSP_LOAD ioctl, and mmap with a crafted offset—are performed by the attacker; no discretionary victim action beyond the device being present in the environment is required.
- S:UScope, unchanged
- Impact is arbitrary read/write of host kernel memory leading to local privilege escalation within the same kernel security authority; it does not cross a VM, container, or IOMMU security boundary.
- C:HConfidentiality impact, high
- Unbounded pgoff arithmetic maps arbitrary kernel struct pages into the attacker's address space; the VMA is not read-only, giving attacker-controlled read access to any reachable kernel page selected via the mmap offset.
- I:HIntegrity impact, high
- The same unbounded mmap fault path installs attacker-chosen kernel pages into a read-write userspace mapping, enabling arbitrary kernel memory writes and heap corruption primitives suitable for privilege escalation or code execution.
- A:HAvailability impact, high
- Large mmap offsets dereference unpopulated vmemmap regions causing kernel paging faults and oops (demonstrated on arm64); arbitrary kernel page writes can also panic the system or destabilize the kernel.