CVE-2026-98676: Linux Kernel Use-After-Free Vulnerability

CVE-2026-98676 Overview

CVE-2026-98676 is a NULL pointer dereference vulnerability in the Linux kernel's Industrial I/O (IIO) subsystem. The flaw resides in the ade9000_setup_clkout() function of the ADE9000 analog-to-digital converter (ADC) driver. The driver passes NULL as the register address when registering a divider clock, causing the common clock framework to dereference an invalid address during rate recalculation. Probing an ADE9000 configured as a clock provider with an external input clock triggers a kernel crash.

Critical Impact
Local denial of service through kernel crash when the ADE9000 driver initializes with an external clock source configured as a clock provider.

Affected Products

Linux kernel versions containing the ADE9000 IIO ADC driver with the vulnerable ade9000_setup_clkout() implementation
Systems with ADE9000 hardware configured as a clock provider using an external input clock
Embedded and industrial Linux deployments using the IIO ADC subsystem for ADE9000 devices

Discovery Timeline

2026-10-18 - CVE-2026-98676 published to NVD
2026-10-19 - Last updated in NVD database

Technical Details for CVE-2026-98676

Vulnerability Analysis

The vulnerability occurs in the ADE9000 IIO ADC driver during clock provider registration. The ade9000_setup_clkout() function registers a divider clock through the common clock framework but supplies NULL as the memory-mapped register address.

During registration, the clock framework invokes clk_divider_recalc_rate(), which attempts to read the divider configuration using readl(). Dereferencing the NULL register pointer triggers an immediate kernel oops. The crash occurs at driver probe time, preventing the device from initializing.

The defect affects only the external clock path. When the ADE9000 uses its internal clock, the driver does not register a clock provider, so the vulnerable code path is not reached.

Root Cause

The root cause is a design mismatch between the hardware behavior and the clock type chosen for registration. CLKOUT on the ADE9000 passes CLKIN through unchanged, so no divider logic or register-backed rate calculation exists in hardware. Registering it as a divider clock caused the framework to expect a valid MMIO register address and dereference it unconditionally.

Attack Vector

The issue manifests at driver probe time on affected hardware configurations. An attacker with the ability to influence device tree configuration, load the kernel module, or physically attach the ADE9000 hardware in the vulnerable configuration can trigger the crash. Remote exploitation is not applicable; this is a local reliability and availability defect in the kernel driver.

The vulnerability is classified as a [CWE-476] NULL Pointer Dereference. Refer to the upstream patch commits for complete technical analysis.

Detection Methods for CVE-2026-98676

Indicators of Compromise

Kernel oops or panic messages referencing clk_divider_recalc_rate or readl during ADE9000 driver probe
Boot failures or dmesg output showing NULL pointer dereference traces originating from the iio-adc-ade9000 module
Repeated probe failures when the device tree configures CLKOUT with an external CLKIN source

Detection Strategies

Inventory Linux systems running IIO ADC drivers and identify kernels that include the ADE9000 driver prior to the upstream fix
Audit device tree sources and overlays for ADE9000 nodes configured with external clock providers
Correlate kernel crash dumps collected through kdump or pstore against the signature of the fault in clk_divider_recalc_rate()

Monitoring Recommendations

Forward dmesg and kernel ring buffer data to a centralized logging platform for anomaly detection on driver probe failures
Monitor fleet-wide kernel version inventory to confirm that patched builds have been deployed to all affected embedded and industrial endpoints
Alert on unexpected device reboots or boot loops on systems hosting ADE9000 hardware

How to Mitigate CVE-2026-98676

Immediate Actions Required

Update to a Linux kernel version that includes the upstream fix registering CLKOUT as a 1:1 fixed-factor clock
For systems that cannot be patched immediately, reconfigure the ADE9000 to use the internal clock, which does not register a clock provider and avoids the vulnerable code path
Validate device tree configurations before deploying new ADE9000-based hardware images

Patch Information

The fix replaces the divider clock registration with a fixed-factor clock registration, which does not require register access. The upstream commits resolving CVE-2026-98676 are available at Kernel Git Commit 134aa31a, Kernel Git Commit 49ee1c6a, and Kernel Git Commit d2400175.

Workarounds

Configure the ADE9000 to use its internal clock source until a patched kernel is deployed
Avoid registering the ADE9000 as a clock provider in device tree configurations on vulnerable kernels
Blacklist the ade9000 driver module on affected systems if the ADC functionality is not required

bash

# Example: blacklist the ADE9000 driver module as a temporary workaround
echo "blacklist ade9000" | sudo tee /etc/modprobe.d/blacklist-ade9000.conf
sudo update-initramfs -u