CVE-2026-98409 in Linux
Summary
by MITRE • 10/14/2026
In the Linux kernel, the following vulnerability has been resolved:
watchdog: rtd119x: Avoid division by zero
clk_get_rate() could return 0. Avoid a division by zero panic.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability resides within the Realtek RTD119x watchdog driver in the Linux kernel, specifically involving improper handling of clock rate retrieval operations. The core technical flaw is rooted in the assumption that the clk_get_rate function will always return a valid, non-zero frequency value for the hardware timer used by the watchdog subsystem. In reality, this function can return zero under various conditions, such as when the associated clock source is disabled, unavailable during early boot stages, or misconfigured within the device tree. When clk_get_rate returns zero and this value is subsequently used in a division operation to calculate timeout intervals or prescaler values for the watchdog timer, it triggers a hardware exception known as a divide-by-zero error. This results in an immediate kernel panic, causing the system to crash and become unresponsive until a manual reboot occurs.
From a security perspective, this vulnerability represents a denial of service condition that can be exploited locally by any user or process with access to the relevant device nodes or configuration interfaces if they can influence the clock state before the watchdog initialization completes. Although it is primarily an availability issue rather than a confidentiality or integrity breach, the impact on system stability is significant for embedded devices relying on this hardware platform. The lack of input validation regarding the return value of critical kernel API calls allows a simple environmental condition to escalate into a complete system failure. This aligns with CWE-369, which describes an error condition that can be exploited to cause a denial of service through division by zero or similar arithmetic errors in software logic.
The operational impact extends beyond immediate crashes; it undermines the reliability of the watchdog mechanism itself. Since the watchdog is designed to detect and recover from system hangs, its own instability due to this bug creates a paradoxical situation where the safety net fails precisely when robustness is most needed. For industrial or critical infrastructure applications utilizing RTD119x chips, such unpredictability can lead to extended downtime and potential data loss if automatic recovery mechanisms are also compromised by the crash. Mitigation strategies must focus on defensive programming practices within the kernel driver code. Developers should implement explicit checks for zero return values from clk_get_rate before performing any arithmetic operations that depend on clock frequency. If a valid rate cannot be obtained, the driver should either defer initialization until the clock is available or fall back to a safe default timeout value rather than proceeding with invalid calculations.
This issue highlights the importance of robust error handling in kernel-space drivers where assumptions about hardware state must never be taken for granted. It also relates to ATT&CK technique T1499, Endpoint Denial of Service, specifically through resource exhaustion or system instability caused by software flaws. To prevent similar vulnerabilities across other subsystems, it is recommended that developers adopt static analysis tools capable of detecting potential division-by-zero scenarios and enforce coding standards that mandate validation of all external inputs, including hardware-reported values like clock rates. Regular auditing of driver code against CWE-369 guidelines will help ensure that future updates to the Linux kernel maintain high availability guarantees even under edge-case hardware configurations or boot sequences.