In the Linux kernel, the following vulnerability has been resolved: timers/migration: Fix off-by-one root mis-connection Before attaching a new root to the old root, the children counter of the new root is checked to verify that only the upcoming CPU's top group have been connected to it. However since the recently added commit b729cc1ec21a ("timers/migration: Fix another race between hotplug and idle entry/exit") this check is not valid anymore because the old root is pre-accounted as a child to the new root. Therefore after connecting the upcoming CPU's top group to the new root, the children count to be expected must be 2 and not 1 anymore. This omission results in the old root to not be connected to the new root. Then eventually the system may run with more than one top level, which defeats the purpose of a single idle migrator. Also the old root is pre-accounted but not connected upon the new root creation. But it can be connected to the new root later on. Therefore the old root may be accounted twice to the new root. The propagation of such overcommit can end up creating a double final top-level root with a groupmask incorrectly initialized. Although harmless given that the final top level roots will never have a parent to walk up to, this oddity opportunistically reported the core issue: WARNING: CPU: 8 PID: 0 at kernel/time/timer_migration.c:543 tmigr_requires_handle_remote CPU: 8 UID: 0 PID: 0 Comm: swapper/8 RIP: 0010:tmigr_requires_handle_remote Call Trace: <IRQ> ? tmigr_requires_handle_remote ? hrtimer_run_queues update_process_times tick_periodic tick_handle_periodic __sysvec_apic_timer_interrupt sysvec_apic_timer_interrupt </IRQ> Fix the problem by taking the old root into account in the children count of the new root so the connection is not omitted. Also warn when more than one top level group exists to better detect similar issues in the future.

The remote Ubuntu 24.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-7491-1 advisory.

    Several security issues were discovered in the Linux kernel. An attacker could possibly use these to     compromise the system. This update corrects flaws in the following subsystems:

    - USB Type-C Connector System Software Interface driver;

    - Timer subsystem; (CVE-2025-21902, CVE-2025-21813)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 24.04 LTS / 24.10 host has a package installed that is affected by a vulnerability as referenced in the USN-7489-1 advisory.

    One security issue was discovered in the Linux kernel. An attacker could possibly use this to compromise     the system. This update corrects flaws in the following subsystems:

    - Timer subsystem; (CVE-2025-21813)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - In the Linux kernel, the following vulnerability has been resolved: timers/migration: Fix off-by-one root     mis-connection Before attaching a new root to the old root, the children counter of the new root is     checked to verify that only the upcoming CPU's top group have been connected to it. However since the     recently added commit b729cc1ec21a (timers/migration: Fix another race between hotplug and idle     entry/exit) this check is not valid anymore because the old root is pre-accounted as a child to the new     root. Therefore after connecting the upcoming CPU's top group to the new root, the children count to be     expected must be 2 and not 1 anymore. This omission results in the old root to not be connected to the new     root. Then eventually the system may run with more than one top level, which defeats the purpose of a     single idle migrator. Also the old root is pre-accounted but not connected upon the new root creation. But     it can be connected to the new root later on. Therefore the old root may be accounted twice to the new     root. The propagation of such overcommit can end up creating a double final top-level root with a     groupmask incorrectly initialized. Although harmless given that the final top level roots will never have     a parent to walk up to, this oddity opportunistically reported the core issue: WARNING: CPU: 8 PID: 0 at     kernel/time/timer_migration.c:543 tmigr_requires_handle_remote CPU: 8 UID: 0 PID: 0 Comm: swapper/8 RIP:
    0010:tmigr_requires_handle_remote Call Trace: <IRQ> ? tmigr_requires_handle_remote ? hrtimer_run_queues     update_process_times tick_periodic tick_handle_periodic __sysvec_apic_timer_interrupt     sysvec_apic_timer_interrupt </IRQ> Fix the problem by taking the old root into account in the children     count of the new root so the connection is not omitted. Also warn when more than one top level group     exists to better detect similar issues in the future. (CVE-2025-21813)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
235364	Ubuntu 24.04 LTS : Linux kernel (OEM) vulnerabilities (USN-7491-1)	Nessus	Ubuntu Local Security Checks	medium
235361	Ubuntu 24.04 LTS / 24.10 : Linux kernel vulnerability (USN-7489-1)	Nessus	Ubuntu Local Security Checks	medium
231504	Linux Distros Unpatched Vulnerability : CVE-2025-21813	Nessus	Misc.	medium

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CVE-2025-21813

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Tenable Plugins

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