CVE-2026-98678 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: adc: ad4030: fix invalid oversampling_ratio validation
In ad4030_set_avg_frame_len(), the logarithm is calculated before input validation. Passing zero or negative values leads to an undefined result from ilog2().
Validate that the input is strictly positive prior to computing its logarithm.
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Analysis
by VulDB Data Team • 10/19/2026
The Linux kernel driver for the Analog Devices AD4030 analog-to-digital converter contains a critical logic error in the function ad4030_set_avg_frame_len, which directly impacts system stability and security posture by allowing invalid configuration parameters to trigger undefined behavior. This vulnerability stems from an improper sequence of operations where mathematical computation is performed before input validation occurs. Specifically, the driver attempts to calculate the base-two logarithm of a user-supplied oversampling ratio using the ilog2 function without first verifying that the value meets basic sanity checks for positive integers.
The technical flaw lies in the absence of pre-condition verification prior to invoking ilog2. In C programming and kernel development, passing zero or negative values to ilog2 results in undefined behavior because the logarithm of non-positive numbers is mathematically undefined within the domain of real integer arithmetic used by this function. When such invalid inputs are processed, the resulting undefined value can propagate through subsequent calculations that depend on the frame length derived from this ratio. This may lead to buffer overflows, incorrect memory allocations, or kernel panics depending on how downstream functions utilize the corrupted data structure associated with the ADC configuration parameters.
From a vulnerability classification perspective, this issue aligns closely with CWE-20 Improper Input Validation and CWE-758 Reliance on Undefined, Unspecified, or Implementation-Specific Behavior. The failure to validate that the oversampling ratio is strictly positive before performing mathematical operations represents a classic case of insufficient boundary checking. In terms of attack vectors, this could potentially be exploited if an attacker has access to the sysfs interface or ioctl calls exposed by the IIO subsystem, allowing them to supply crafted negative or zero values to trigger kernel instability. This maps to ATT&CK techniques involving driver-level exploitation where local privilege escalation might be attempted through denial-of-service conditions leading to system crashes or potential code execution if memory corruption occurs as a side effect of undefined behavior.
The operational impact of this vulnerability includes the risk of immediate kernel panic upon device configuration attempts with invalid parameters, resulting in service disruption for systems relying on high-precision ADC measurements. In embedded environments where reliability is paramount, such instability can compromise safety-critical applications that depend on consistent sensor data acquisition. Furthermore, if the undefined behavior leads to memory corruption, it opens avenues for more severe security breaches including arbitrary code execution with kernel privileges.
Mitigation strategies involve applying the upstream Linux kernel patch that reorders the validation logic within ad4030_set_avg_frame_len. The fix ensures that input parameters are checked for positivity before any logarithmic calculations are attempted. System administrators should update their kernels to versions containing this correction and enforce strict parameter validation in custom applications interacting with IIO devices. Additionally, developers integrating AD4030 drivers into new designs should implement defensive programming practices by validating all hardware configuration inputs against expected ranges prior to passing them to kernel subsystems, thereby preventing similar vulnerabilities from arising due to improper input handling sequences.