CVE-2026-68214 Overview
CVE-2026-68214 is a use-after-free vulnerability in the Linux kernel's rtl2832 DVB-T demodulator driver. The flaw resides in the rtl2832_remove() function, where cancel_delayed_work_sync() is invoked before i2c_mux_del_adapters(). This ordering allows a concurrent I2C transfer path to reschedule i2c_gate_work after the cancellation completes, leading to a use-after-free when kfree(dev) releases the driver context.
Critical Impact
A race condition between device removal and in-flight I2C mux transfers can trigger a use-after-free on the freed dev structure, potentially resulting in kernel memory corruption or denial of service.
Affected Products
- Linux kernel media/dvb-frontends/rtl2832 driver
- Systems using RTL2832-based DVB-T USB tuner hardware
- Kernel branches referenced by the upstream stable fix commits
Discovery Timeline
- 2026-08-10 - CVE-2026-68214 published to the National Vulnerability Database (NVD)
- 2026-08-10 - Last updated in NVD database
Technical Details for CVE-2026-68214
Vulnerability Analysis
The rtl2832 driver exposes an I2C multiplexer adapter used by tuner chips such as r820t. During probe, r820t_attach() performs I2C transfers through the mux. Each transfer passes through i2c_mux_master_xfer(), which calls rtl2832_deselect() after the transfer completes. rtl2832_deselect() re-arms i2c_gate_work using schedule_delayed_work().
In rtl2832_remove(), the original ordering called cancel_delayed_work_sync() first and then i2c_mux_del_adapters(). cancel_delayed_work_sync() waits for any currently running instance to complete, but it does not prevent a later, unrelated code path from queuing the work again. If an I2C transfer is still in flight on another thread, rtl2832_deselect() can reschedule i2c_gate_work after the cancel has returned. The remove path then proceeds to release the device context with kfree(dev), and the delayed work later fires against freed memory.
Root Cause
The root cause is an incorrect teardown ordering in rtl2832_remove(). The mux adapter remains registered while worker cancellation runs, so the deselect callback can requeue the delayed work after the sync cancel completes. This is a classic Use-After-Free ([CWE-416]) driven by a race between removal and concurrent driver activity.
Attack Vector
Exploitation requires local access with the ability to trigger probe and remove sequences on an RTL2832-based device, typically by attaching or detaching a USB DVB-T tuner or by binding and unbinding the driver through sysfs. An attacker who can win the race between an in-flight r820t_attach() I2C transfer and driver removal can cause the kernel to dereference freed memory. Successful triggering results in kernel memory corruption or a kernel panic. Remote exploitation is not applicable to this bug.
No public proof-of-concept is currently available. Refer to the upstream commits for the exact code paths involved, including Kernel Git Commit 24bef23 and Kernel Git Commit 9acd5bb.
Detection Methods for CVE-2026-68214
Indicators of Compromise
- Kernel oops or panic traces referencing i2c_gate_work, rtl2832_deselect, or the rtl2832 module during device unbind or USB detach events.
- KASAN reports flagging use-after-free reads or writes inside delayed work execution originating from the rtl2832 driver.
- Repeated bind/unbind or USB re-enumeration of DVB-T tuner devices in system logs immediately preceding kernel faults.
Detection Strategies
- Enable CONFIG_KASAN on test kernels to surface the use-after-free deterministically during driver stress testing.
- Monitor dmesg and journal logs for stack traces containing rtl2832_remove, cancel_delayed_work_sync, or kfree near delayed work handlers.
- Correlate kernel crashes with USB hotplug events for devices exposing the RTL2832 chipset.
Monitoring Recommendations
- Ingest kernel logs and crash dumps into a centralized logging pipeline for pattern matching against the affected symbols.
- Alert on unexpected module load or unload activity for dvb_usb_rtl28xxu and rtl2832 on production hosts.
- Track running kernel versions across the fleet and flag hosts still on unpatched stable branches.
How to Mitigate CVE-2026-68214
Immediate Actions Required
- Apply the vendor-supplied kernel update that reorders rtl2832_remove() to call i2c_mux_del_adapters() before cancel_delayed_work_sync().
- Restrict physical and logical access to USB ports on systems where untrusted users could attach RTL2832-based tuners.
- Prevent unprivileged users from binding or unbinding kernel drivers via sysfs on affected hosts.
Patch Information
The upstream fix moves i2c_mux_del_adapters() ahead of cancel_delayed_work_sync() in rtl2832_remove(). Once the mux adapter is unregistered, no new I2C transfers can traverse it, so rtl2832_deselect() can no longer reschedule i2c_gate_work, and the subsequent cancel is final. The fix is available in the following commits: Kernel Git Commit 24bef23, Kernel Git Commit 2c71bda, Kernel Git Commit 680daf4, Kernel Git Commit 90d7817, and Kernel Git Commit 9acd5bb.
Workarounds
- Blacklist the rtl2832 and dvb_usb_rtl28xxu modules on systems that do not require DVB-T functionality until patched kernels are deployed.
- Disable USB hotplug for untrusted devices via udev rules or USBGuard policies to prevent race triggering.
- Avoid manual driver unbind operations on affected hardware while the system is under I2C transfer load.
# Configuration example: prevent the vulnerable driver from loading
echo 'blacklist rtl2832' | sudo tee /etc/modprobe.d/cve-2026-68214.conf
echo 'blacklist dvb_usb_rtl28xxu' | sudo tee -a /etc/modprobe.d/cve-2026-68214.conf
sudo depmod -a
sudo update-initramfs -u
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
