CVE-2026-68223 Overview
CVE-2026-68223 is a memory leak vulnerability in the Linux kernel's Amlogic Meson video decoder (meson_vdec) media driver. The flaw resides in the vdec_open() function, which failed to release the mem-to-mem (m2m) context when vdec_init_ctrls() returned an error. Each failed open call leaked kernel memory allocated by v4l2_ctrl_handler_init_class(), as confirmed via kmemleak diagnostics. The issue affects Linux systems using the Meson VDEC driver, typically Amlogic-based ARM64 platforms exposing V4L2 video decode devices.
Critical Impact
Repeated failed calls to open the video decode device leak kernel memory, enabling a local unprivileged user to exhaust kernel resources over time and degrade system stability.
Affected Products
- Linux kernel builds including the meson_vdec media driver
- Amlogic Meson SoC platforms exposing V4L2 decoder character devices
- Distributions shipping affected stable branches prior to the referenced fix commits
Discovery Timeline
- 2026-08-10 - CVE-2026-68223 published to NVD
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68223
Vulnerability Analysis
The vulnerability is a kernel memory leak [CWE-401] in the error-handling path of vdec_open() inside the Meson VDEC V4L2 driver. When vdec_init_ctrls() fails during device open, control flow jumps directly to the err_m2m_release label. That label releases the m2m device but skips releasing the associated m2m context previously allocated by v4l2_m2m_ctx_init(). As a result, each failed open path leaks the m2m context and its control handler allocations.
The kmemleak backtrace confirms the leaked allocation originates from v4l2_ctrl_handler_init_class() invoked through vdec_open+0x1f4/0x788, reachable via v4l2_open() and chrdev_open() when userspace opens the decoder character device. A local attacker who can open the V4L2 decoder node and trigger control initialization failures can leak kernel memory repeatedly. Sustained exploitation contributes to resource exhaustion and impacts long-running embedded systems.
Root Cause
The root cause is an incomplete cleanup sequence in the vdec_open() error path. The function allocated the m2m context before calling vdec_init_ctrls() but did not include a cleanup label that released the context on control initialization failure. The fix introduces a new err_m2m_ctx_release label that calls v4l2_m2m_ctx_release(sess->m2m_ctx) prior to releasing the m2m device, restoring the correct unwind order.
Attack Vector
The vulnerability requires local access to the affected system and permission to open the Meson VDEC V4L2 device node. An attacker triggers the leak by repeatedly opening the decoder device under conditions that cause vdec_init_ctrls() to fail. Each failed open leaks a small kernel allocation. Because the vulnerability is a resource-exhaustion issue rather than a memory-corruption primitive, it does not yield direct code execution or privilege escalation.
Detailed exploitation code is not required beyond repeated invocation of the vulnerable open path. Refer to the upstream fix commits for technical context on the corrected error-unwind sequence.
Detection Methods for CVE-2026-68223
Indicators of Compromise
- Recurring kmemleak reports referencing v4l2_ctrl_handler_init_class and vdec_open in the allocation backtrace.
- Steady growth in kernel slab usage attributable to v4l2 control-handler allocations on Amlogic Meson devices.
- Repeated failed open() syscalls against /dev/video* nodes exposed by the meson_vdec driver.
Detection Strategies
- Enable CONFIG_DEBUG_KMEMLEAK on test builds and monitor /sys/kernel/debug/kmemleak for the signature backtrace shown in the advisory.
- Track kernel version and module load state for meson_vdec across the fleet to identify unpatched hosts.
- Correlate audit logs of openat() syscalls against V4L2 device nodes with kernel memory growth metrics.
Monitoring Recommendations
- Alert on abnormal frequency of failing open() calls to /dev/video* from non-service accounts.
- Watch /proc/meminfo and SReclaimable/SUnreclaim slab counters for sustained upward drift on Meson-based devices.
- Ingest kernel logs into a centralized platform to search for kmemleak and V4L2 subsystem warnings across affected hosts.
How to Mitigate CVE-2026-68223
Immediate Actions Required
- Update to a Linux kernel that includes the upstream fix commits referenced in the kernel.org stable tree.
- Restrict access to /dev/video* decoder nodes to trusted user groups using standard udev rules and file permissions.
- Audit which local users and containers can open the Meson VDEC device on affected hardware.
Patch Information
The fix adds an err_m2m_ctx_release label to vdec_open() that releases the m2m context via v4l2_m2m_ctx_release(sess->m2m_ctx) before releasing the m2m device. Backports are available across multiple stable kernel branches. See the upstream commits: 1391b75, 2cf0171, 940f161, 99f3527, and c6cd08a.
Workarounds
- Unload the meson_vdec module (modprobe -r meson_vdec) on systems that do not require hardware video decoding.
- Tighten permissions on /dev/video* nodes so only trusted media services can open the decoder.
- Reboot periodically on long-running embedded devices where patching is not yet feasible to reclaim leaked kernel memory.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
