---
id: "CVE-2026-98935"
kind: "vulnerability"
aliases: ["CVE-2026-98935"]
title: "Linux kernel: RTC wakeup alarm ioctl can leak stack memory"
severity: "unknown"
cvss: null
epss: 0.00209
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "kernel", "linux", "rtc"]
not_affected_if: []
published_at: "2026-10-23T13:17:14+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98935", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-98935", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: RTC wakeup alarm ioctl can leak stack memory

The Linux kernel's RTC device ioctl returned a struct with padding holes that could contain uninitialized kernel stack data. The fix zero-initializes the struct so no stack bytes reach userspace.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98935
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-98935

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

rtc: dev: zero-initialize struct rtc_wkalrm to prevent information leak

The struct rtc_wkalrm has padding holes after the 'pending' member.
When returned to userspace via the RTC_WKALRM_RD ioctl, uninitialized
kernel stack data residing in these holes may be leaked.

Zero-initialize the struct at declaration to eliminate this information
leak risk.

Fixes smatch warnings:
- drivers/rtc/dev.c:392 rtc_dev_ioctl() warn: check that 'alarm' doesn't
  leak information (struct has a hole after 'pending')

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_