CVE-2026-53384 Overview
CVE-2026-53384 is a use-after-free vulnerability in the Linux kernel's 8250_dw serial driver. The flaw resides in the dw8250_probe() function, which registers an 8250 port through serial8250_register_8250_port() and subsequently attempts to register a clock notifier. When clk_notifier_register() fails, the probe returns an error but leaves the 8250 port registered. The devm-allocated driver data is freed while the port still references it through the saved private_data and serial_in/serial_out callbacks. Any subsequent access to that port slot before a rebind constitutes a use-after-free condition affecting kernel memory integrity.
Critical Impact
A use-after-free in a registered serial port slot can lead to kernel memory corruption, potential privilege escalation, and system compromise on affected Linux systems.
Affected Products
- Linux kernel builds including the 8250_dw (Synopsys DesignWare 8250) serial driver
- Systems using DesignWare UART hardware with clock notifier support
- Distributions shipping vulnerable kernel versions prior to the referenced stable commits
Discovery Timeline
- 2026-07-19 - CVE-2026-53384 published to NVD
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-53384
Vulnerability Analysis
The vulnerability originates in the probe path of the 8250_dw driver. dw8250_probe() performs two sequential registration steps. First, it registers the serial port with serial8250_register_8250_port(), which stores driver-managed private data referenced through the port's private_data field and its serial_in/serial_out I/O callbacks. Second, if the device has a clock, the probe calls clk_notifier_register() to register a notifier.
When clk_notifier_register() fails, the probe function returns the error code directly without unwinding the earlier port registration. The corresponding serial8250_unregister_port() call exists only in dw8250_remove(), which the kernel does not invoke when probe fails. The port slot therefore remains occupied by a stale registration.
Because the driver data was allocated with the device-managed allocator (devm_*), the kernel automatically frees it once probe returns an error. The still-registered port continues to reference this freed memory through its callback pointers and private data. Subsequent access to the port slot, for example via /dev/ttyS* or /proc/tty/driver/serial, dereferences freed memory and triggers the use-after-free condition.
Root Cause
The root cause is an error-handling omission. The probe function lacks a cleanup step to call serial8250_unregister_port() on the clk_notifier_register() failure path. Combined with devm-managed lifetime of the driver's private data, the mismatch between port registration lifetime and private-data lifetime produces the dangling reference.
Attack Vector
Triggering the flaw requires the clk_notifier_register() call to fail during probe of a 8250_dw device. Any process or subsystem that reads from or writes to the residual port slot can then dereference the freed devm-allocated memory. The upstream fix, distributed across the referenced stable commits including 07ffe414, 10fc708b, 3d205fe8, 511d2b92, 778b9dda, ccdf4510, and d72650a4, calls serial8250_unregister_port() on the error path before returning.
No verified public exploit code is available. See the referenced kernel stable commits for the corrective patches.
Detection Methods for CVE-2026-53384
Indicators of Compromise
- Kernel log entries showing dw8250 probe failures accompanied by clk_notifier_register errors followed by later oops or panic messages referencing 8250 port callbacks
- KASAN or KFENCE reports flagging use-after-free reads or writes within serial8250_* or dw8250_* symbols
- Unexpected kernel crashes when userspace opens or queries serial device nodes on affected hardware
Detection Strategies
- Enable CONFIG_KASAN on test and staging kernels to surface use-after-free access in the 8250 port slot during boot and device rebind cycles
- Audit installed kernel package versions against the fixed commit hashes referenced in the vendor advisories to identify unpatched systems
- Correlate probe-failure log lines with subsequent serial subsystem faults using centralized logging
Monitoring Recommendations
- Forward dmesg and journald kernel logs to a centralized log platform and alert on dw8250 probe errors
- Track kernel package inventory across the fleet and flag hosts running versions prior to the fix
- Monitor for unexpected reboots or kernel panics on hosts with DesignWare UART hardware
How to Mitigate CVE-2026-53384
Immediate Actions Required
- Update affected Linux systems to a kernel version that includes one of the fix commits: 07ffe414, 10fc708b, 3d205fe8, 511d2b92, 778b9dda, ccdf4510, or d72650a4
- Prioritize patching on embedded and server platforms that use DesignWare UART controllers and rely on clock notifier registration
- Restrict access to serial device nodes (/dev/ttyS*) to trusted users until patched kernels are deployed
Patch Information
The upstream fix modifies dw8250_probe() to call serial8250_unregister_port() when clk_notifier_register() returns an error, ensuring the port slot is released before the devm-managed private data is freed. Refer to the Kernel Git Commit 07ffe41 and the additional stable branch backports listed in the CVE references for the exact source changes.
Workarounds
- Disable the 8250_dw driver module on systems that do not require DesignWare UART support by blacklisting it in /etc/modprobe.d/
- Restrict permissions on serial character devices to prevent unprivileged access to potentially stale port slots
- Rebind or reboot affected devices after any observed probe failure to clear the vulnerable port state until a patched kernel is installed
# Blacklist the 8250_dw module until a patched kernel is available
echo "blacklist 8250_dw" | sudo tee /etc/modprobe.d/blacklist-8250_dw.conf
sudo update-initramfs -u
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
