CVE-2022-41218

What it actually does

Use-after-free in Linux kernel DVB demux driver caused by refcount races between dvb_demux_open and dvb_dmxdev_release, resulting in local denial of service.

Why it matters to the business

Linux systems with DVB hardware can experience kernel crashes and reboots, leading to service interruptions on media or broadcast servers.

How an attack unfolds

An attacker with local access triggers concurrent DVB demux open and release operations to exploit the refcount race, freeing memory that is later accessed and causing a kernel panic.

How to fix it

Update the Linux kernel to the commit fd3d91ab1c6ab0628fe642dd570b56302c30a792 or later stable release containing the fix; rebuild and deploy the updated kernel image.

How to confirm the fix worked

Verify the kernel source contains commit fd3d91ab1c6ab0628fe642dd570b56302c30a792, boot the new kernel, and confirm DVB demux operations no longer trigger crashes under concurrent load.

Typical attack path

1. Obtain local shell on affected Linux system
2. Load or access DVB demux device nodes
3. Trigger parallel calls to dvb_demux_open and dvb_dmxdev_release
4. Induce use-after-free dereference leading to kernel crash

How to detect it

Review kernel logs for use-after-free warnings or oops traces referencing dmxdev.c or dvb_dmxdev_release around the time of unexpected reboots.

What your security team should do

• Prioritize kernel upgrade on all systems exposing DVB devices
• Apply the fix within standard maintenance windows given the local attack requirement
• Monitor vendor advisories for backported patches in distribution kernels