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CVE-2026-68204
media: vivid: check for vb2_is_busy() when toggling caps
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/media. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68204 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 | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The vivid_update_format_cap/out() functions must only be called if the capture/output queue are not busy. But for the controls that select the CROP/COMPOSE/SCALE capability that is not checked. Only when streaming starts will they be set to 'grabbed' and it is impossible to change the control, but between REQBUFS and STREAMON you are still allowed to set these controls. Since vivid_update_format_cap/out will change the format, this can cause unexpected results. Besides adding these checks, also add a WARN_ON in vivid_update_format_cap/out() if the queue is busy. I'm 90% certain that this is the cause of this syzbot bug: https://syzkaller.appspot.com/bug?extid=dac8f5eaa46837e97b89 But since we never have reproducers, it is hard to be certain. In any case, these checks are needed regardless.
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.
drivers/media/test-drivers/vivid/vivid-ctrls.c
drivers/media/test-drivers/vivid/vivid-vid-cap.c
drivers/media/test-drivers/vivid/vivid-vid-out.c
- What this is
- VIVID VIRTUAL VIDEO DRIVERMAINTAINERS section matched on drivers/media/test-drivers/vivid/* · linux-media@vger.kernel.org · Maintained
- Kernel module
- vivid
Check it on the machine
grep -w CONFIG_VIDEO_VIVID /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 vividPrints 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/cloud-arm64
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- 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 switch
- CONFIG_VIDEO_VIVID
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
- 2026-08-10 (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
- 0.18%, higher than 6.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/media
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.18 | 5.10.265 | 0a820f03727b |
| 3.18 | 5.15.216 | bbc96bc75de0 |
| 3.18 | 6.1.183 | 6a5bc8aea111 |
| 3.18 | 6.6.148 | a9cd0e8fb0b2 |
| 3.18 | 6.12.101 | abaec6747304 |
| 3.18 | 6.18.42 | 492c97cb50fe |
| 3.18 | 7.1.6 | daf2d92669b4 |
| 3.18 | 7.2 | c2d1a2130c93 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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 purely through local ioctls (VIDIOC_REQBUFS/PREPARE_BUF/S_EXT_CTRLS/STREAMON) on the /dev/videoN character device exposed by the vivid driver. There is no remote or network component.
- AC:LAttack complexity, low
- The attacker fully controls both the initial buffer allocation size and the later geometry change, so the undersized-buffer overflow is produced deterministically by a fixed ioctl sequence with no race or memory-layout precondition.
- PR:LPrivileges required, low
- No capability check exists on the V4L2 control or buffer ioctls; any process able to open /dev/videoN can trigger it, which on desktops/Android and container images with video devices bind-mounted means an ordinary unprivileged user (video group / logind ACL).
- UI:NUser interaction, none
- The entire sequence is performed by the attacking process itself against a device node it opens; no victim action or cooperation is needed.
- S:UScope, unchanged
- The corruption stays within the kernel's own memory and security authority; no VM, IOMMU or sandbox boundary is crossed by the overflow itself.
- C:HConfidentiality impact, high
- The stale-geometry mismatch also drives out-of-bounds reads on the output path and lets adjacent kernel allocations be read back through the mmap'ed plane, and the resulting heap corruption can be shaped into a broader kernel-memory disclosure primitive.
- I:HIntegrity impact, high
- The capture kthread writes a full frame using the enlarged geometry into a plane allocated for the smaller format, giving an out-of-bounds kernel write of attacker-chosen length and largely attacker-influenced (test-pattern) content, which is exploitable for kernel memory corruption.
- A:HAvailability impact, high
- Overwriting memory past the vb2 plane reliably corrupts neighbouring allocations or hits a vmalloc guard page, producing KASAN splats, oopses and kernel panics; the post-fix WARN_ON also panics on panic_on_warn systems.