CVE-2026-74547 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (adt7470) Fix busy-loop and I2C flooding in update thread
When userspace configures 'auto_update_interval' to 0 via sysfs, the background kthread executes schedule_timeout_interruptible(0), which returns immediately.
If 'num_temp_sensors' is concurrently or previously set to 0, the msleep_interruptible() delay inside adt7470_read_temperatures() also becomes 0. This combination forces the background thread into a tight, unbounded busy-loop, hogging the CPU and flooding the I2C bus with a continuous stream of transactions.
Fix this vulnerability by raising the lower limit of the clamp_val in auto_update_interval_store() from 0 to 500 milliseconds. This guarantees a reasonable minimum sleep window between sensor updates, protecting the system from intentional or accidental I2C bus denial of service.
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Analysis
by VulDB Data Team • 08/16/2026
The vulnerability described represents a critical race condition and resource exhaustion issue within the Linux kernel's hardware monitoring subsystem, specifically affecting the adt7470 hardware monitor driver. This flaw demonstrates how seemingly innocuous configuration parameters can lead to severe system instability and denial of service conditions when not properly validated. The issue occurs in the context of hardware monitoring where the kernel maintains background threads to periodically read temperature sensor data from hardware components connected via I2C bus interfaces. When userspace applications configure the auto_update_interval parameter to zero through sysfs interfaces, the driver's internal logic fails to account for this edge case properly.
The technical implementation flaw stems from improper validation of user-provided values within the kernel's configuration handling code. Specifically, when the auto_update_interval is set to zero, the schedule_timeout_interruptible(0) function call immediately returns without any delay, while concurrent or previous setting of num_temp_sensors to zero causes msleep_interruptible() to also execute with zero delay. This creates a pathological condition where the background kernel thread enters an unbounded busy-loop executing continuously without any meaningful delays between iterations. The combination of these two zero-valued conditions effectively removes all temporal boundaries from the sensor reading loop, causing the thread to consume 100% CPU cycles in an infinite tight loop.
The operational impact of this vulnerability extends beyond simple resource consumption to represent a potential denial of service attack vector against the entire system. The continuous I2C bus flooding generated by the busy-loop creates a scenario where legitimate hardware communication becomes impossible, as the bus becomes overwhelmed with repeated transactions. This condition can affect not only temperature monitoring functionality but potentially compromise other I2C devices sharing the same bus, leading to cascading failures throughout the system's hardware monitoring capabilities. The vulnerability also aligns with ATT&CK technique T1499.001 which involves resource exhaustion attacks, and CWE-362 represents the concurrency issue that enables this race condition to occur.
The proposed fix addresses the core validation problem by implementing a minimum threshold of 500 milliseconds for the auto_update_interval configuration parameter. This change ensures that even in the worst-case scenario where userspace provides an invalid zero value, the system maintains reasonable temporal boundaries between sensor updates. The solution follows security best practices by establishing a minimum acceptable delay that prevents both accidental misconfiguration and intentional abuse of the system resources. This approach effectively mitigates the tight loop condition while maintaining functional compatibility with legitimate use cases that require periodic sensor monitoring. The fix demonstrates proper input validation principles that align with kernel security guidelines, ensuring that all user-provided configuration values are properly bounded to prevent system-level resource exhaustion conditions.
The vulnerability highlights important lessons about defensive programming in kernel space where improper boundary checking can lead to severe system instability. It emphasizes the critical need for parameter validation in kernel drivers, particularly when dealing with timing-related parameters that control background thread execution. The fix also demonstrates how simple threshold enforcement can provide robust protection against both accidental misconfiguration and malicious exploitation attempts targeting system resources. This vulnerability serves as a reminder of the importance of considering all possible combinations of user inputs and system states when designing kernel-level software components, particularly those controlling hardware interfaces where resource contention can have widespread system impacts.