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CVE-2026-64134
ALSA: pcm: Don't setup bogus iov_iter for silencing
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem sound/core. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64134 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
At transition to the iov_iter for PCM data transfer, we blindly applied the iov_iter setup also for silencing (i.e. data = NULL), and it leads to a calculation of bogus iov_iter. Fortunately this didn't cause troubles on most of architectures but it goes wrong on RISC-V now, causing a NULL dereference. Handle the NULL data case to treat the silencing in interleaved_copy() for addressing the bug above. noninterleaved_copy() has already the NULL data handling, so it doesn't need changes.
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/core/pcm_lib.c
- What this is
- SOUNDMAINTAINERS section matched on sound/ · linux-sound@vger.kernel.org · Maintained
- Kernel module
- snd_pcm
Check it on the machine
grep -wE 'CONFIG_SND|CONFIG_SND_PCM' /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_pcmPrints 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, sidMnot 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_PCM
- 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
- 2026-07-19 (3 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 2.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- sound/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.6 | 6.6.142 | 41a766c64729 |
| 6.6 | 6.12.92 | ce836587e594 |
| 6.6 | 6.18.34 | feff0251386a |
| 6.6 | 7.0.11 | c9f676851581 |
| 6.6 | 7.1 | e4d3386b74fb |
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 vulnerable code is reached only via local ALSA PCM interfaces—opening `/dev/snd/pcmC*D*p`, `write()`/`ioctl()` on that device, or OSS PCM emulation—not via any network-facing kernel protocol.
- AC:LAttack complexity, low
- An attacker with PCM device access can reliably trigger silencing by setting `silence_size > 0` via `SNDRV_PCM_IOCTL_SW_PARAMS`, using OSS playback (which auto-enables silence), calling `snd_pcm_lib_write()` with a NULL buffer, or starting playback so `snd_pcm_playback_silence()` runs on interleaved streams.
- PR:LPrivileges required, low
- Exploitation requires a local process able to open and configure a PCM playback stream (typically any logged-in desktop/mobile user with audio device access via the `audio` group, seat ACL, or equivalent permissions), not root or special capabilities.
- UI:NUser interaction, none
- Triggering the bug requires only programmatic PCM playback/silencing operations; no victim interaction such as mounting a filesystem or opening a malicious file is needed.
- S:UScope, unchanged
- Impact is confined to kernel memory safety within the ALSA PCM subsystem on the local host; it does not cross a security boundary such as VM escape, sandbox escape, or IOMMU bypass.
- C:HConfidentiality impact, high
- Passing `data=NULL` through `do_transfer()` constructs a bogus `iov_iter` with a NULL base pointer; this is a kernel memory-safety defect in the iterator layer that can cause out-of-bounds or NULL-based reads when iterator helpers dereference the malformed state, not merely a benign error return.
- I:HIntegrity impact, high
- The same bogus `iov_iter` setup supplies invalid source/destination metadata to the kernel copy path; if iterator operations proceed on the malformed structure, uncontrolled kernel writes are possible, and the identical NULL-handling gap in `noninterleaved_copy()` confirms this silencing path was always meant to bypass `do_transfer()`.
- A:HAvailability impact, high
- On RISC-V the defect manifests as a kernel NULL pointer dereference during silencing, causing an oops/panic and denial of service; the bug is also reachable on every architecture where interleaved PCM silencing is used.