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Linux KernelOperating system · Linux

CVE-2025-39953

MEDIUM · 5.5 CVSS v3.1 Published 2025-10-04
Fix available
A fix is available. Upgrade to 5.4.300 / 5.10.245 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch 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: cgroup: split cgroup_destroy_wq into 3 workqueues A hung task can occur during [1] LTP cgroup testing when repeatedly mounting/unmounting perf_event and net_prio controllers with systemd.unified_cgroup_hierarchy=1. The hang manifests in cgroup_lock_and_drain_offline() during root destruction. Related case: cgroup_fj_function_perf_event cgroup_fj_function.sh perf_event cgroup_fj_function_net_prio cgroup_fj_function.sh net_prio Call Trace: cgroup_lock_and_drain_offline+0x14c/0x1e8 cgroup_destroy_root+0x3c/0x2c0 css_free_rwork_fn+0x248/0x338 process_one_work+0x16c/0x3b8 worker_thread+0x22c/0x3b0 kthread+0xec/0x100 ret_from_fork+0x10/0x20 Root Cause: CPU0 CPU1 mount perf_event umount net_prio cgroup1_get_tree cgroup_kill_sb rebind_subsystems // root destruction enqueues // cgroup_destroy_wq // kill all perf_event css // one perf_event css A is dying // css A offline enqueues cgroup_destroy_wq // root destruction will be executed first css_free_rwork_fn cgroup_destroy_root cgroup_lock_and_drain_offline // some perf descendants are dying // cgroup_destroy_wq max_active = 1 // waiting for css A to die Problem scenario: 1. CPU0 mounts perf_event (rebind_subsystems) 2. CPU1 unmounts net_prio (cgroup_kill_sb), queuing root destruction work 3. A dying perf_event CSS gets queued for offline after root destruction 4. Root destruction waits for offline completion, but offline work is blocked behind root destruction in cgroup_destroy_wq (max_active=1) Solution: Split cgroup_destroy_wq into three dedicated workqueues: cgroup_offline_wq – Handles CSS offline operations cgroup_release_wq – Manages resource release cgroup_free_wq – Performs final memory deallocation This separation eliminates blocking in the CSS free path while waiting for offline operations to complete. [1] https://github.com/linux-test-project/ltp/blob/master/runtest/controllers

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

A detailed technical summary for this CVE is being prepared.

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.

NVD · CPE data
Linux KernelOperating system
Affected:>= 4.6, < 5.4.300>= 5.5, < 5.10.245>= 5.11, < 5.15.194>= 5.16, < 6.1.154>= 6.2, < 6.6.108>= 6.7, < 6.12.49>= 6.13, < 6.16.9= 6.17

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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 available Upgrade to 5.4.300 / 5.10.245 / 5.15.194 or later
Fixed in 5.4.3005.10.2455.15.194
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel version 5.4.300, 5.10.245, 5.15.194, 6.1.154, or any later stable release (e.g., 6.6.y, 6.12.y)

  1. Identify the currently running Linux kernel version using 'uname -r'
  2. Determine which affected version range your kernel falls into (>= 4.6 to < 5.4.300, >= 5.5 to < 5.10.245, >= 5.11 to < 5.15.194, or >= 5.16 to < 6.1.154)
  3. For RHEL/CentOS systems: Update kernel via 'yum update kernel' or 'dnf update kernel', then reboot to the new kernel version
  4. For Debian/Ubuntu systems: Update via 'apt-get update && apt-get upgrade linux-image-generic' or 'apt-get dist-upgrade', then reboot
  5. For SUSE systems: Use 'zypper patch' or 'zypper update kernel-*', then reboot
  6. Verify the fix is applied by checking the kernel version after reboot matches or exceeds the fixed release (5.4.300, 5.10.245, 5.15.194, or 6.1.154)
Caveat Kernel upgrades may require driver recompilation or system downtime; ensure critical modules are compatible with the new kernel version

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-39953 in production — separate from our analysis above.

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