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CVE-2026-89885
media: platform: mtk-mdp3: Fix SCP device refcounting
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/media. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89885 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 | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
mdp_probe() first tries to get the SCP handle with scp_get(). When that fails, it falls back to looking up the SCP platform device with __get_pdev_by_id() and then reads its driver data. The fallback lookup returns the platform device with a reference, just like scp_get() does. However, the fallback path currently drops that reference immediately after platform_get_drvdata(). The driver later still calls scp_put(mdp->scp) unconditionally from the probe error path and from mdp_video_device_release(), which drops the SCP device reference again. Keep the fallback reference until the existing scp_put() call, so that the fallback path follows the same ownership rules as the scp_get() path.
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/platform/mediatek/mdp3/mtk-mdp3-core.c
- What this is
- MEDIA INPUT INFRASTRUCTURE (V4L/DVB)MAINTAINERS section matched on drivers/media/ · linux-media@vger.kernel.org · Maintained
- Kernel module
- mtk_mdp3
Check it on the machine
grep -w CONFIG_VIDEO_MEDIATEK_MDP3 /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 mtk_mdp3Prints 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 does not build this code in 1 release. It does build it in 4 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k
- n
- not enabled on any flavour - this release does not build the code
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_VIDEO_MEDIATEK_MDP3
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
- 2026-09-16 (33 days 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
- 0.20%, higher than 8.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.12.64 | 6.12.110 | dce13bd9bade |
| 6.18.4 | 6.18.51 | 252850653569 |
| 6.19 | 7.2.5 | 0259ade4c4ce |
| 6.19 | 7.3 | 55793e4665b7 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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 extra put_device is in mdp_probe()/mdp_video_device_release of the MediaTek MDP3 platform driver, reached only via local driver-model bind on MT8183/MT8195 (boot, deferred probe, module load, or sysfs rebind). No network, Bluetooth/Wi-Fi, or USB path reaches this SCP refcounting.
- AC:LAttack complexity, low
- On MT8183 the MDP RDMA node has no mediatek,scp phandle, so scp_get() fails and the compatible fallback is the production path. That path drops the of_find_device_by_node() ref then later scp_put() extra-puts; cmdq mailbox EPROBE_DEFER after the fallback makes this deterministic with no race.
- PR:NPrivileges required, none
- mdp_probe() runs in driver-core context with no capable() or credential check. On MediaTek Chromebooks, phones, and embedded boards, MDP3 commonly deferred-probes at boot after the SCP fallback, so the extra put fires without a user account.
- UI:NUser interaction, none
- Platform probe and deferred-probe retries run unattended at boot or module bind on affected hardware. Opening /dev/video, mounting a filesystem, or plugging a device is not required.
- S:UScope, unchanged
- The extra put_device() use-after-free is of the host SCP platform_device inside the same kernel security authority. It does not cross a VM, IOMMU/DMA, or sandbox boundary.
- C:HConfidentiality impact, high
- scp_put() extra-puts the SCP platform_device, which can run device_release and free the still-bound struct device. A use-after-free of that object enables reclaim and kernel-memory disclosure.
- I:HIntegrity impact, high
- The same device UAF is heap corruption of struct platform_device/mtk_scp still used by the SCP driver and other scp_get() holders, enabling heap spray, arbitrary write, and control-flow hijack.
- A:HAvailability impact, high
- Freeing the SCP device while it remains registered, or later dereferencing the dangling scp pointer from MDP3/vcodec, causes a kernel oops or panic.