In the Linux kernel, the following vulnerability has been resolved: rtc: dev: zero-initialize struct rtc_wkalrm to prevent information leak The… (CVE-2026-98935)

The Linux kernel contained a vulnerability where the struct rtc_wkalrm, used in the RTC driver, had padding holes after the 'pending' member that were not zero-initialized. When this struct was returned to userspace through the RTC_WKALRM_RD ioctl, uninitialized kernel stack data in these padding holes could be leaked. The fix involved zero-initializing the struct at declaration to prevent this information leak. This change also addressed smatch static analysis warnings related to potential information leaks in rtc_dev_ioctl().

The vulnerability could allow an attacker with access to the RTC_WKALRM_RD ioctl interface to obtain uninitialized kernel stack data, potentially leaking sensitive kernel memory contents. There is no indication of code execution or privilege escalation. The impact is limited to information disclosure.

An official fix has been applied to the Linux kernel source code to zero-initialize the struct rtc_wkalrm, preventing the information leak. Users should update to the fixed kernel version containing this patch. No additional mitigation is required beyond applying the official fix.