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

Patch nowHigh7.8Exploited, CISA due date 2025-09-25EPSS 1.4%, higher than 72% of scored CVEs

CVE-2025-38352 is a time-of-check to time-of-use race in Linux Kernel, rated high (7.8 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published · Updated · NVD status: Analyzed

What it is

Something is checked, then changed by an attacker before it is used.

How it is reached

An attacker can exploit it by someone who can already run code or sign in on the machine, with an ordinary user account, and nobody has to click anything.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline. In practice, this kind of flaw lets an attacker win a timing window to bypass a check or corrupt shared state.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2025-09-04: it is being exploited in the wild. EPSS estimates a 1.4% chance of exploitation activity in the next 30 days, higher than 72% of scored CVEs.

What to do

  1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2025-09-25.
  2. No fixed version is listed for Linux Kernel itself; fixed versions for the other affected products are listed on this page.
  3. Limit who can run code or sign in on the hosts that run it.
  4. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

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.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
  • Request handlers and jobs that share state. The flaw sits between concurrent requests or processes.

Trust boundaries in play

  • Host boundary. The attacker needs a foothold on the machine first; the flaw turns a small foothold into a bigger one.
  • Between concurrent requests or processes. An attacker who crosses it can win a timing window to bypass a check or corrupt shared state.

Questions to answer about your own systems

  • Where does Linux Kernel run in your systems, and at which version?
  • Which of those hosts also run code or users you do not fully trust?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

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Exploits and proofs of concept

Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.