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CVE-2026-89873
media: v4l2-ctrls: validate HEVC EXT SPS RPS counts
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-2026-89873 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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. |
The vulnerability
What the bug is
The HEVC SPS control carries the short-term and long-term RPS counts that decoder drivers use to walk the matching EXT SPS dynamic arrays. Reject SPS values that exceed the HEVC limits of 64 short-term sets and 32 long-term references so drivers cannot later index beyond those controls. Also reject EXT SPS ST RPS entries whose negative or positive picture counts exceed the 16-entry arrays, or whose combined delta-POC count exceeds the HEVC DPB maximum.
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/v4l2-core/v4l2-ctrls-core.c
- What this is
- MEDIA INPUT INFRASTRUCTURE (V4L/DVB)MAINTAINERS section matched on drivers/media/ · linux-media@vger.kernel.org · Maintained
- Kernel module
- videodev
Check it on the machine
grep -w CONFIG_VIDEO_DEV /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 videodevPrints 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 switch
- CONFIG_VIDEO_DEV
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
- 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
- 0.17%, higher than 5.4% 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 |
|---|---|---|
| 7.0 | 7.2.5 | 30f85a7c5911 |
| 7.0 | 7.3 | 796b5c6d4f16 |
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 only through the local V4L2 interface on a stateless HEVC decoder node (/dev/videoN) via VIDIOC_S_EXT_CTRLS plus request-API QBUF/STREAMON. There is no remote or network-facing path into the HEVC SPS or EXT SPS RPS controls.
- AC:LAttack complexity, low
- The attacker supplies num_short_term_ref_pic_sets, num_long_term_ref_pics_sps, num_negative_pics, and num_positive_pics as unconstrained u8 values; any out-of-range count deterministically drives rkvdec HEVC RPS assembly out of bounds on the next decode run. No race, timing window, or uncontrollable memory layout is involved.
- PR:LPrivileges required, low
- Only an unprivileged local account with access to the video device node is required (typically the video group, or the media/codec service on Android and embedded Rockchip devices). rkvdec_open() and rkvdec_hevc_validate_sps() check neither capabilities nor the RPS counts.
- UI:NUser interaction, none
- The attacking process performs the entire sequence itself: open the decoder, set the crafted HEVC SPS and EXT SPS RPS controls, queue buffers, and start streaming. No victim action, media file, or mount is needed.
- S:UScope, unchanged
- The out-of-bounds accesses stay inside the kernel's own slab and coherent DMA memory within the same security authority. No VM, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- rkvdec_hevc_prepare_hw_st_rps() indexes ext_sps_st_rps[] with an attacker-chosen u8 count up to 255 against a 64-entry (or smaller dynamic) array, and st_ref_pic_set_calculate() reads delta_poc_s0_minus1[] past its 16-entry field, leaking adjacent kernel heap into the decode path.
- I:HIntegrity impact, high
- st_ref_pic_set_calculate() writes used_by_curr_pic_s0[]/delta_poc_s0[] with a u8 loop bound up to 255 into 16-entry arrays on a kzalloc object, and rkvdec_set_bw_field() writes RPS bitfields for set index i>63 past the end of the rps DMA object into adjacent priv_tbl memory.
- A:HAvailability impact, high
- The heap overflow of calculated_rps_st_sets and the DMA-table bitfield writes can walk into unmapped or poisoned memory and trip KASAN/hardening checks, producing a kernel oops, and can wedge the decoder hardware; the trigger is repeatable at will.