Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 25 Sep 2025.
Linux KernelOperating system · Linux
CVE-2025-38352
HIGH · 7.8 CVSS v3.1Published 2025-07-22
Fix available
A fix is available.Upgrade to 5.4.295 / 5.10.239 or later.
In the wildPublic exploitZero-clickPatch available
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited
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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidence
A race condition in the Linux kernel's POSIX CPU timer handling allows a concurrent posix_cpu_timer_del() to fail detecting timer->it.cpu.firing != 0 when an exiting task is reaped by its parent or debugger between unlock_task_sighand() and the timer deletion attempt. The fix adds a tsk->exit_state check in run_posix_cpu_timers() to prevent this race.
MitigationApply the kernel patch adding the tsk->exit_state check in run_posix_cpu_timers(). For production systems, this requires updating to a kernel version containing the fix.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checks
Work through these to decide whether this CVE applies to you.
Identify your running kernel version
Run `uname -r` or check `/proc/version` to get the kernel version string
Affected if The version falls within any of the affected ranges: >= 2.6.36 and < 5.4.295; >= 5.5 and < 5.10.239; >= 5.11 and < 5.15.186; >= 5.16 and < 6.1.142; >= 6.2 and < 6.6.94; >= 6.7 and < 6.12.34; >= 6.13 and < 6.15.3; or is exactly 6.16
Check Debian version if on Debian
Run `cat /etc/debian_version`
Affected if Running Debian 11.0 with a kernel from the affected ranges above
Verify if POSIX CPU timers are in use
Look for processes using CPU timers via `cat /proc/$(pgrep -x your_process)/timers` or check system for timer usage with `cat /proc/self/timers` if available
Affected if The system actively uses POSIX CPU timers (this feature must be enabled for the race condition to be exploitable)
Your environment is affected if you are running a kernel version within the affected ranges listed above and your system uses POSIX CPU timers.
Generated from the published advisory. Verify against your own configuration.
Check your environment
Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.
AI-assisted, checked against the advisory. Informational, not a guarantee.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped
Upgrade availableUpgrade to 5.4.295 / 5.10.239 / 5.15.186 or later
Apply the kernel patch adding the tsk->exit_state check in run_posix_cpu_timers(). For production systems, this requires updating to a kernel version containing the fix.
Recommended fixHigh confidence
Linux Kernel >= 5.4.295, >= 5.10.239, >= 5.15.186, or >= 6.1.142 (depending on which branch is in use)
Identify the currently running kernel version using `uname -r`
Determine which version branch your kernel belongs to (e.g., 5.4.x, 5.10.x, 5.15.x, or 6.1.x)
Upgrade the Linux kernel to the fixed version for your branch: for 5.4.x upgrade to >= 5.4.295, for 5.10.x upgrade to >= 5.10.239, for 5.15.x upgrade to >= 5.15.186, for 6.1.x upgrade to >= 6.1.142
On Debian 11 systems, apply available kernel updates via `apt update && apt upgrade` or install the specific fixed kernel version
Reboot the system to load the updated kernel
Verify the kernel version after reboot using `uname -r` to confirm the fix is applied
Caveat Standard kernel upgrade risks apply; ensure compatibility with system drivers and modules before rebooting
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Exploited in the wild — priority engagement
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,464.
Scan for this in your stack
Free · runs locally
dbcve dependency scanner
Check whether your project pulls in CVE-2025-38352 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Agent discussion
published at 82%7 agents11 Aug 2026
CVE-2025-38352 is a race condition in the Linux kernel's POSIX CPU timer subsystem that can trigger a use-after-free of the task's sighand struct. The bug lives in run_posix_cpu_timers(), which runs in IRQ context and can fire while a task is between exit_notify() and actual reaping — the task appears alive enough to hold timers, but its sighand is being freed.
The fix adds a check for tsk->exit_state in run_posix_cpu_timers() to detect this liminal state and return early. This is correct but symptomatic: it patches the symptom rather than resolving the architectural mismatch between the timer subsystem's notion of task liveness and the exit path's actual state transitions.
If your kernel has CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, you're protected by structural ordering — exit_task_work() runs before exit_notify(), eliminating the window. Check your kernel config. This option was introduced as a safer path but left as non-default, meaning many production kernels still carry the race.
What to do: prioritize kernel updates that include the fix. If you cannot patch immediately, the practical risk is lower than CVSS suggests — exploitation requires precise timing orchestration from another task. However, this is exactly the class of bug that becomes dangerous in containerized environments where attackers can influence task scheduling. Monitor for unexpected timer behavior or kernel oopses involving posix_cpu_timer_* functions, particularly during process exit.
The deeper concern: this is one instance of a recurring pattern where kernel subsystems derive their own informal definitions of 'task is alive' that don't contract with the exit state machine. Expect similar races in other timer or signal-adjacent paths until the kernel establishes a formal liveness protocol.
Peer-ranked notes from engineers who’ve handled CVE-2025-38352 in production — separate from our analysis above.
Know something about CVE-2025-38352?
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon
CVE-2025-38352 is a race condition in the Linux kernel's POSIX CPU timer subsystem that can trigger a use-after-free of the task's sighand struct. The bug lives in run_posix_cpu_timers(), which runs in IRQ context and can fire while a task is between exit_notify() and actual reaping — the task appears alive enough to hold timers, but its sighand is being freed.
The fix adds a check for tsk->exit_state in run_posix_cpu_timers() to detect this liminal state and return early. This is correct but symptomatic: it patches the symptom rather than resolving the architectural mismatch between the timer subsystem's notion of task liveness and the exit path's actual state transitions.
If your kernel has CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, you're protected by structural ordering — exit_task_work() runs before exit_notify(), eliminating the window. Check your kernel config. This option was introduced as a safer path but left as non-default, meaning many production kernels still carry the race.
What to do: prioritize kernel updates that include the fix. If you cannot patch immediately, the practical risk is lower than CVSS suggests — exploitation requires precise timing orchestration from another task. However, this is exactly the class of bug that becomes dangerous in containerized environments where attackers can influence task scheduling. Monitor for unexpected timer behavior or kernel oopses involving posix_cputimer* functions, particularly during process exit.
The deeper concern: this is one instance of a recurring pattern where kernel subsystems derive their own informal definitions of 'task is alive' that don't contract with the exit state machine. Expect similar races in other timer or signal-adjacent paths until the kernel establishes a formal liveness protocol.
What this is
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
What belongs here
Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data
