CVE-2026-89883: Linux Kernel Privilege Escalation Vulnerability

CVE-2026-89883 Overview

CVE-2026-89883 is a resource management flaw in the Linux kernel's Allwinner Sunxi Consumer Infrared (sunxi-cir) remote control driver. The defect resides in the driver probe function within the media/rc subsystem. After rc_register_device() succeeds, subsequent probe failures jump to an allocation cleanup label that only calls rc_free_device(). This leaves the registered rc device and its associated kernel resources allocated and reachable. The stale registration constitutes a kernel resource leak and can leave dangling references to freed memory during error unwinding.

Critical Impact
A local attacker able to trigger probe failure conditions on affected sunxi-cir hardware paths can leak kernel resources and potentially corrupt kernel state, leading to loss of confidentiality, integrity, and availability on the local system.

Affected Products

Linux kernel builds including the drivers/media/rc/sunxi-cir.c driver
Allwinner Sunxi platforms exposing the Consumer Infrared receiver
Stable kernel branches referenced by the fix commits listed in the kernel.org advisory

Discovery Timeline

2026-09-16 - CVE-2026-89883 published to the National Vulnerability Database (NVD)
2026-09-16 - Last updated in the NVD database

Technical Details for CVE-2026-89883

Vulnerability Analysis

The sunxi-cir driver initializes an infrared receiver device during platform probe. The probe sequence allocates an rc_dev structure, populates it, then calls rc_register_device() to publish the device to the kernel's remote control core. After registration, the driver performs IRQ lookup, IRQ request, and hardware initialization. Any failure in these post-registration steps executes a goto that reaches only the allocation cleanup label. That label invokes rc_free_device(), which is appropriate before registration but incorrect afterward. Once rc_register_device() succeeds, the correct teardown call is rc_unregister_device(), which both removes the device from the RC core and releases its resources. The mismatch leaves a registered device tied to freed or partially initialized driver state.

Root Cause

The root cause is an incorrect error-unwind path in the driver's probe function. The code lacks a distinct label to unregister the device when failures occur after rc_register_device() returns success. The fix introduces a separate unwind label for the IRQ lookup, IRQ request, and hardware initialization failure paths, ensuring rc_unregister_device() runs when needed while preserving rc_free_device() for earlier failures.

Attack Vector

Exploitation requires local access with low privileges on a system exposing the sunxi-cir driver. An attacker who can influence probe conditions, such as through module load, device rebinding via sysfs, or induced hardware initialization failures, can trigger the flawed error path. The resulting resource leak and stale registration can be leveraged for denial of service and, depending on kernel allocator state, for further memory corruption primitives affecting kernel integrity.

No public exploit code is documented in the CVE record. The technical details of the fix are available in the Linux Kernel Commit 4655a59 and related stable branch commits.

Detection Methods for CVE-2026-89883

Indicators of Compromise

Repeated sunxi-cir probe failure messages in dmesg or the systemd journal, especially entries referencing IRQ lookup or hardware initialization errors
Growth in kernel slab allocations for rc_dev or associated RC core objects without corresponding release events
Unexpected residual entries under /sys/class/rc/ after driver unbind on Allwinner platforms

Detection Strategies

Inventory Linux hosts running Allwinner Sunxi hardware and confirm whether the sunxi_cir module is loaded
Query package management data to identify kernel versions that predate the fix commits referenced on kernel.org
Correlate driver probe error log lines with subsequent kernel memory pressure or module rebind attempts

Monitoring Recommendations

Ship kernel logs to a centralized analytics platform and alert on repeated sunxi-cir probe failures
Track /proc/slabinfo trends on affected devices to identify unbounded growth of RC-related caches
Monitor module load, unload, and driver bind and unbind events through auditd rules on production Linux fleets

How to Mitigate CVE-2026-89883

Immediate Actions Required

Apply the upstream patches referenced by kernel.org, including Linux Kernel Commit 479aa6f and Linux Kernel Commit 4efd714, through your distribution's kernel update channel
Restrict local shell access on Allwinner Sunxi devices to trusted administrators
Disable automatic driver rebinding for sunxi-cir where the infrared receiver is not required

Patch Information

The fix adds a dedicated unwind label that calls rc_unregister_device() when probe steps after registration fail, and retains rc_free_device() for earlier failures. Patched commits are published across multiple stable branches, including Linux Kernel Commit 59951b8, Linux Kernel Commit 5b58d8c, Linux Kernel Commit 5e6f5bf, and Linux Kernel Commit 826763a. Rebuild and deploy vendor kernels that include these commits.

Workarounds

Unload the sunxi_cir module on systems that do not require infrared input, using modprobe -r sunxi_cir
Blacklist the module in /etc/modprobe.d/ on affected platforms until a patched kernel is deployed
Limit access to sysfs bind and unbind interfaces to root only, and audit any tooling that manipulates driver binding

bash

# Configuration example: blacklist sunxi_cir until a patched kernel is installed
echo 'blacklist sunxi_cir' | sudo tee /etc/modprobe.d/cve-2026-89883.conf
sudo modprobe -r sunxi_cir 2>/dev/null || true
sudo update-initramfs -u