CVE-2026-68356 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
watchdog: airoha: Prevent division by zero when clock frequency is zero
clk_get_rate() can return 0 when the clock provider is not properly configured or the clock is unmanaged. The driver uses wdt_freq as a divisor directly in airoha_wdt_probe() to compute max_timeout and in airoha_wdt_get_timeleft() to compute the remaining time, which results in a division by zero.
Add a check for wdt_freq == 0 in probe and return -EINVAL with dev_err_probe() to prevent the division by zero and provide a diagnostic message.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability identified in the Linux kernel watchdog subsystem affects the airoha watchdog driver, representing a critical division by zero condition that could lead to system instability or denial of service. This flaw occurs when the clk_get_rate() function returns zero, indicating an improperly configured or unmanaged clock provider. The airoha watchdog driver directly utilizes the wdt_freq variable as a divisor in two critical functions during driver initialization and operation, creating an inherent risk of arithmetic exceptions when clock frequency information is unavailable or invalid.
The technical implementation of this vulnerability stems from insufficient input validation within the driver's probe function where the wdt_freq value is obtained without proper verification of its validity. When clk_get_rate() returns zero due to missing clock configuration or hardware issues, the subsequent computation in airoha_wdt_probe() for max_timeout calculation and in airoha_wdt_get_timeleft() for remaining time computation directly employs this zero value as a divisor. This mathematical error violates fundamental programming practices and creates an exploitable condition that can cause kernel panics or system crashes.
From an operational perspective, this vulnerability presents significant risks to embedded systems and devices relying on the airoha watchdog functionality for system monitoring and automatic reboot capabilities. The division by zero condition can trigger immediate system instability during driver initialization, preventing proper watchdog functionality and potentially leaving critical systems without protective mechanisms. This affects not only the specific airoha hardware but also demonstrates broader concerns about clock management and error handling in kernel subsystems that depend on external timing sources.
The mitigation strategy implemented addresses this vulnerability through defensive programming techniques that align with established security practices and industry standards. The solution incorporates explicit validation checks for wdt_freq == 0 during driver probe operations, returning -EINVAL error codes with appropriate diagnostic messages using dev_err_probe() function calls. This approach follows the principle of fail-fast design patterns recommended in software security best practices and directly addresses the CWE-369 vulnerability category related to division by zero errors. The implementation also conforms to ATT&CK framework considerations for kernel-level vulnerabilities, specifically addressing the techniques associated with privilege escalation and system stability compromise through improper input validation.
The fix demonstrates proper error handling methodology that prevents cascading failures while maintaining system diagnostic capabilities. By implementing early detection and graceful failure mechanisms, the solution ensures that driver initialization terminates appropriately when clock configuration issues are detected, preventing the propagation of invalid state information throughout the watchdog subsystem. This defensive approach aligns with the principle of least privilege and robust system design, ensuring that kernel components fail gracefully rather than causing system-wide disruptions. The resolution also reinforces proper clock management practices within embedded Linux systems, emphasizing the critical importance of validating hardware abstraction layer interfaces before utilizing timing information in critical system functions.