Bug 2521470 (CVE-2026-74687)

Summary: CVE-2026-74687 kernel: watchdog: at91sam9_wdt: prevent timer rearm during teardown
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel, specifically within the `at91sam9_wdt` watchdog timer driver. During the driver's teardown process, the `at91_ping()` function could rearm the watchdog timer. However, the `timer_delete()` function does not prevent this, resulting in a use-after-free vulnerability where the timer attempts to access memory that has already been released. This flaw could be triggered by a local attacker or specific system conditions, potentially leading to system instability or a denial of service.
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Description OSIDB Bzimport 2026-08-22 15:47:08 UTC 
In the Linux kernel, the following vulnerability has been resolved:

watchdog: at91sam9_wdt: prevent timer rearm during teardown

at91_ping() rearms the watchdog timer from its callback. timer_delete()
neither waits for a running callback nor prevents it from rearming the
timer, so probe failure or driver removal can leave the timer accessing the
devm-allocated at91wdt after it has been freed.

Use timer_shutdown_sync() on both teardown paths. It waits for a running
callback and rejects any attempt by the callback to rearm the timer.
Comment 1 Keith Grant 2026-08-24 16:58:22 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082233-CVE-2026-74687-b615@gregkh/T