CVE-2026-63935 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: adc: nxp-sar-adc: fix division by zero in write_raw
Add a validation check for the sampling frequency value before using it as a divisor. A user writing zero or a negative value to the sampling_frequency sysfs attribute triggers a division by zero in the kernel.
Also prevent unsigned integer underflow when the computed cycle count is smaller than NXP_SAR_ADC_CONV_TIME, which would wrap the u32 inpsamp to a huge value.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability in question affects the Linux kernel's industrial I/O subsystem specifically within the nxp-sar-adc driver implementation. This issue represents a critical security flaw that arises from insufficient input validation mechanisms within the device driver's write_raw function. The vulnerability manifests when userspace applications interact with the sampling_frequency sysfs attribute, which exposes internal ADC configuration parameters to user-level processes.
The core technical flaw stems from a division by zero condition that occurs when the sampling frequency value is set to zero or negative values through the sysfs interface. This primitive error in input validation creates an immediate kernel panic scenario where the divisor parameter becomes invalid, leading to system instability and potential denial of service conditions. The vulnerability directly maps to CWE-369, which addresses division by zero errors in software implementations, and also aligns with CWE-129, concerning improper validation of array indices or buffer bounds.
When a user writes zero or negative values to the sampling_frequency attribute, the kernel code attempts to perform arithmetic operations using this invalid parameter as a divisor, causing an immediate system crash. Additionally, the vulnerability encompasses an unsigned integer underflow scenario that occurs when computing cycle counts during ADC conversion processes. Specifically, when the computed cycle count falls below the predefined NXP_SAR_ADC_CONV_TIME constant, the u32 variable inpsamp undergoes underflow and wraps around to produce extremely large values.
This integer underflow condition creates a secondary vulnerability where malicious input can cause unexpected behavior in subsequent calculations or memory operations within the ADC driver. The wraparound effect transforms what should be a small cycle count into a massive unsigned integer value that could lead to buffer overflows, memory corruption, or other unpredictable system states during ADC conversion cycles.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to potentially enable privilege escalation attacks or information disclosure mechanisms. Attackers could exploit this weakness to crash the kernel or manipulate ADC conversion timing parameters in ways that might compromise data integrity or system stability. The vulnerability affects systems utilizing NXP SAR ADC hardware configurations and can be exploited through normal user-space applications that have access to the sysfs interface.
Mitigation strategies should focus on implementing robust input validation at multiple levels within the driver codebase. The primary fix requires adding explicit validation checks for sampling frequency values before any mathematical operations are performed, ensuring that zero and negative values are rejected with appropriate error codes. Additionally, bounds checking must be implemented for cycle count calculations to prevent unsigned integer underflow conditions, particularly when dealing with hardware-specific timing constants like NXP_SAR_ADC_CONV_TIME.
Security hardening measures should also include implementing proper error handling within the write_raw function to gracefully reject invalid inputs rather than allowing kernel execution to proceed with malformed parameters. The fix must align with security best practices outlined in the ATT&CK framework under defense evasion techniques, specifically targeting privilege escalation and denial of service attack vectors that could be leveraged through kernel-level vulnerabilities.
System administrators should ensure all affected systems are updated with patched kernel versions containing the validation checks and integer overflow protections. Regular monitoring of sysfs attribute access patterns can help detect potential exploitation attempts targeting this specific vulnerability class. The solution must maintain backward compatibility while introducing comprehensive input sanitization to prevent both division by zero conditions and unsigned integer underflow scenarios that compromise system integrity and stability.