Bug 2513144 (CVE-2026-68357)

Summary: CVE-2026-68357 kernel: watchdog: pretimeout: Fix UAF in watchdog_unregister_governor()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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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's watchdog subsystem. When a watchdog governor is unregistered, if it is also set as the default governor, the default governor is not properly cleared. This can lead to a Use-After-Free (UAF) condition where new or existing watchdog devices may inherit or be reassigned a dangling pointer. This vulnerability could result in system instability or a denial of service.
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Description OSIDB Bzimport 2026-08-10 12:21:38 UTC 
In the Linux kernel, the following vulnerability has been resolved:

watchdog: pretimeout: Fix UAF in watchdog_unregister_governor()

When a watchdog governor is unregistered, it updates existing watchdog
devices that were using this governor by falling back to `default_gov`.

If the governor being unregistered is currently set as `default_gov`,
the `default_gov` is never cleared.  This leads to 2 use-after-free
issues:
1. New watchdog devices registered after this point will inherit the
   dangling `default_gov`.
2. Existing watchdog devices using the unregistered governor will have
   their `wdd->gov` reassigned to the dangling `default_gov`.

Fix the UAF by clearing `default_gov` if it matches the governor being
unregistered.
Comment 1 gkamathe 2026-08-11 10:45:14 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081040-CVE-2026-68357-c18c@gregkh/T