CVE-2026-68206: media: v4l2-ctrls: validate HEVC active reference counts

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

media: v4l2-ctrls: validate HEVC active reference counts

HEVC slice parameters are shared stateless V4L2 controls, but the common
validation path does not verify the active L0/L1 reference counts before
driver-specific code consumes them.

The original report came from Cedrus, but the active count bounds are
not Cedrus-specific. Validate them in the common HEVC slice control path
so stateless HEVC drivers get the same basic guarantees as soon as the
control is queued.

Do not reject ref_idx_l0/ref_idx_l1 entries here. Existing userspace may
use out-of-range sentinel values such as 0xff for missing references, and
some hardware can use that information for concealment. Keep this common
check limited to the active reference counts.

The Linux kernel CVE team has assigned CVE-2026-68206 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.14 with commit d395a78db9eabd12633b39e05c80e803543b6590 and fixed in 6.6.148 with commit 9a998cc1c348769262d433acb7d238c5fac4b2e0
	Issue introduced in 5.14 with commit d395a78db9eabd12633b39e05c80e803543b6590 and fixed in 6.12.101 with commit dbaf0e0023e2f9332c5164822def7f80b7d2c5ef
	Issue introduced in 5.14 with commit d395a78db9eabd12633b39e05c80e803543b6590 and fixed in 6.18.42 with commit 3068ab802fc98b121dcb451e1f7f4d338ffc7a19
	Issue introduced in 5.14 with commit d395a78db9eabd12633b39e05c80e803543b6590 and fixed in 7.1.6 with commit b01df98a6669d2b67d8aed816021b327fd905998
	Issue introduced in 5.14 with commit d395a78db9eabd12633b39e05c80e803543b6590 and fixed in 7.2-rc1 with commit afbe4bc252d90a6f8fad869b06d5430f615f22f9

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-68206
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/media/v4l2-core/v4l2-ctrls-core.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9a998cc1c348769262d433acb7d238c5fac4b2e0
	https://git.kernel.org/stable/c/dbaf0e0023e2f9332c5164822def7f80b7d2c5ef
	https://git.kernel.org/stable/c/3068ab802fc98b121dcb451e1f7f4d338ffc7a19
	https://git.kernel.org/stable/c/b01df98a6669d2b67d8aed816021b327fd905998
	https://git.kernel.org/stable/c/afbe4bc252d90a6f8fad869b06d5430f615f22f9