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Actively exploited

CVE-2025-38352 Linux Kernel Time-of-Check Time-of-Use (TOCTOU) Race Condition Vulnerability

Linux kernel contains a time-of-check time-of-use (TOCTOU) race condition vulnerability that has a high impact on confidentiality, integrity, and availability.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 4 Sep 2025.
  • Rated High severity (CVSS 7.8, scored by Vendor).
  • It has been in the catalogue for 428 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() If an exiting non-autoreaping task has already passed exit_notify() and calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent or debugger right after unlock_task_sighand(). If a concurrent posix_cpu_timer_del() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or lock_task_sighand() will fail. Add the tsk->exit_state check into run_posix_cpu_timers() to fix this. This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because exit_task_work() is called before exit_notify(). But the check still makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail anyway in this case.

Affected Versions

ProductVersions
Linux Linux0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before 78a4b8e3795b31dae58762bc091bb0f4f74a2200
0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before c076635b3a42771ace7d276de8dc3bc76ee2ba1b
0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before 2f3daa04a9328220de46f0d5c919a6c0073a9f0b
0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before 764a7a5dfda23f69919441f2eac2a83e7db6e5bb
0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before 2c72fe18cc5f9f1750f5bc148cf1c94c29e106ff
0bdd2ed4138ec04e09b4f8165981efc99e439f55 to before c29d5318708e67ac13c1b6fc1007d179fb65b4d7
Linux Linux2.6.36

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Linux Kernel. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 25 Sep 2025 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

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All 32 exploited Linux vulnerabilities

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2025-38352
  3. CVE record: CVE-2025-38352
  4. FIRST EPSS
  5. source.android.com/docs/security/bulletin/2025-09-01
  6. git.kernel.org/stable/c/78a4b8e3795b31dae58762bc091bb0f4f74a2200
  7. git.kernel.org/stable/c/c076635b3a42771ace7d276de8dc3bc76ee2ba1b
  8. git.kernel.org/stable/c/2f3daa04a9328220de46f0d5c919a6c0073a9f0b
  9. git.kernel.org/stable/c/764a7a5dfda23f69919441f2eac2a83e7db6e5bb
  10. git.kernel.org/stable/c/2c72fe18cc5f9f1750f5bc148cf1c94c29e106ff
  11. git.kernel.org/stable/c/c29d5318708e67ac13c1b6fc1007d179fb65b4d7
  12. git.kernel.org/stable/c/460188bc042a3f40f72d34b9f7fc6ee66b0b757b