CVE-2026-68206: Undefined Security Weakness

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.