CVE-2026-98676 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: adc: ade9000: fix NULL pointer dereference in clkout registration
ade9000_setup_clkout() passes NULL as the register address when registering a divider clock. During clock registration, the common clock framework calls clk_divider_recalc_rate(), which dereferences the address through readl(). As a result, probing an ADE9000 configured as a clock provider with an external input clock crashes.
CLKOUT passes CLKIN through without changing its rate. Register it as a 1:1 fixed-factor clock, which does not require register access.
This change does not affect the configuration using the internal clock, for which the driver does not register a clock provider.
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Analysis
by VulDB Data Team • 10/19/2026
The vulnerability identified in the Linux kernel involves a critical NULL pointer dereference within the Industrial I/O subsystem, specifically affecting the ADE9000 analog-to-digital converter driver. This flaw occurs during the initialization phase when the system attempts to configure and register output clocks for devices that operate as clock providers with an external input source. The root cause lies in the function ade9000_setup_clkout(), which incorrectly passes a NULL value for the hardware register address parameter required by the common clock framework. This misconfiguration triggers a sequence of operations where the kernel attempts to recalculate and verify the clock rate, leading directly to a system crash if not addressed.
From a technical perspective, the defect is rooted in improper handling of pointer arguments during device driver registration. When the ADE9000 is configured as a clock provider using an external input clock, the driver invokes clk_divider_recalc_rate() through the common clock framework infrastructure. This function expects a valid memory-mapped I/O address to read hardware registers and determine current clock frequencies. However, because the register address pointer remains NULL, any attempt by readl() or similar low-level access functions to dereference this null location results in an immediate kernel panic. Such errors typically manifest as oops messages followed by system halts, rendering the device unusable until a reboot occurs with corrected software.
The operational impact of this vulnerability is significant for systems relying on stable clocking mechanisms provided by ADE9000-based hardware. In production environments where high availability and continuous operation are required, such kernel crashes can lead to service interruptions, data loss during active conversions, or complete system unresponsiveness. Engineers deploying these chips in industrial automation, energy monitoring, or medical imaging applications must ensure that their firmware and driver stacks do not trigger this specific code path under external clock configurations. The instability compromises the reliability of timing-critical processes dependent on precise clock signals generated by the ADC device.
To mitigate this issue, developers have implemented a structural change to how CLKOUT is registered within the kernel space. Instead of attempting to register it as a divider clock that requires dynamic rate calculation via hardware register access, the solution reclassifies CLKOUT as a 1:1 fixed-factor clock. This approach bypasses the need for any readl() operations since the output frequency simply mirrors the input without modification. By eliminating the dependency on volatile memory addresses during registration, the driver avoids triggering NULL pointer exceptions entirely while maintaining functional equivalence in terms of signal propagation characteristics.
This remediation aligns with best practices outlined in CWE-476, which classifies improper null pointer dereferences as a common software weakness leading to denial-of-service conditions. Furthermore, from an adversarial perspective, if this vulnerability were exploitable remotely or through local privilege escalation vectors, it could be categorized under ATT&CK techniques related to system availability disruption via resource exhaustion or crash induction. Although currently limited to configuration-time crashes rather than runtime exploitation by malicious actors, the fix ensures robustness against accidental misconfigurations that mimic such failure modes.
It is important to note that this correction specifically targets scenarios involving external input clocks where the device acts as a clock provider. Configurations utilizing internal clocks remain unaffected because they do not involve registering the ADE9000 as a clock provider in the same manner, thereby avoiding the problematic code path altogether. This selective application of fixes demonstrates precision engineering aimed at resolving specific edge cases without introducing regressions into other operational modes of the driver.
System administrators and kernel maintainers should apply patches containing this fix to ensure stability across all supported hardware configurations involving ADE9000 devices. Regular updates to the Linux kernel are essential for maintaining security posture against both known vulnerabilities and potential future exploits arising from similar coding patterns in peripheral drivers. Monitoring system logs for clock-related initialization failures can help identify instances where older, vulnerable versions of the driver might still be in use within legacy deployments.