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Linux KernelOperating system · Linux

CVE-2026-52991

HIGH · 7.8 CVSS v3.1 Published 2026-06-24
Fix available
A fix is available. Upgrade to 6.18.33 / 7.0.10 or later.
See remediation →
80/100
Remediation priority · High
Zero-click 8 weeks old

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: sched/psi: fix race between file release and pressure write A potential race condition exists between pressure write and cgroup file release regarding the priv member of struct kernfs_open_file, which triggers the uaf reported in [1]. Consider the following scenario involving execution on two separate CPUs: CPU0 CPU1 ==== ==== vfs_rmdir() kernfs_iop_rmdir() cgroup_rmdir() cgroup_kn_lock_live() cgroup_destroy_locked() cgroup_addrm_files() cgroup_rm_file() kernfs_remove_by_name() kernfs_remove_by_name_ns() vfs_write() __kernfs_remove() new_sync_write() kernfs_drain() kernfs_fop_write_iter() kernfs_drain_open_files() cgroup_file_write() kernfs_release_file() pressure_write() cgroup_file_release() ctx = of->priv; kfree(ctx); of->priv = NULL; cgroup_kn_unlock() cgroup_kn_lock_live() cgroup_get(cgrp) cgroup_kn_unlock() if (ctx->psi.trigger) // here, trigger uaf for ctx, that is of->priv The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards the memory deallocation of of->priv performed within cgroup_file_release(). However, the operations involving of->priv executed within pressure_write() are not entirely covered by the protection of cgroup_mutex. Consequently, if the code in pressure_write(), specifically the section handling the ctx variable executes after cgroup_file_release() has completed, a uaf vulnerability involving of->priv is triggered. Therefore, the issue can be resolved by extending the scope of the cgroup_mutex lock within pressure_write() to encompass all code paths involving of->priv, thereby properly synchronizing the race condition occurring between cgroup_file_release() and pressure_write(). And, if an live kn lock can be successfully acquired while executing the pressure write operation, it indicates that the cgroup deletion process has not yet reached its final stage; consequently, the priv pointer within open_file cannot be NULL. Therefore, the operation to retrieve the ctx value must be moved to a point *after* the live kn lock has been successfully acquired. In another situation, specifically after entering cgroup_kn_lock_live() but before acquiring cgroup_mutex, there exists a different class of race condition: CPU0: write memory.pressure CPU1: write cgroup.pressure=0 =========================== ============================= kernfs_fop_write_iter() kernfs_get_active_of(of) pressure_write() cgroup_kn_lock_live(memory.pressure) cgroup_tryget(cgrp) kernfs_break_active_protection(kn) ... blocks on cgroup_mutex cgroup_pressure_write() cgroup_kn_lock_live(cgroup.pressure) cgroup_file_show(memory.pressure, false) kernfs_show(false) kernfs_drain_open_files() cgroup_file_release(of) kfree(ctx) of->priv = NULL cgroup_kn_unlock() ... acquires cgroup_mutex ctx = of->priv; // may now be NULL if (ctx->psi.trigger) // NULL dereference Consequently, there is a possibility that of->priv is NULL, the pressure write needs to check for this. Now that the scope of the cgroup_mutex has been expanded, the original explicit cgroup_get/put operations are no longer necessary, this is because acquiring/releasing the live kn lock inherently executes a cgroup get/put operation. [1] BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 Call Trace: pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:43 ---truncated---

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 Linux kernel's sched/psi (Pressure Stall Information) causes use-after-free of the priv member in struct kernfs_open_file. The cgroup_mutex doesn't fully protect operations on of->priv, allowing cgroup_file_release() to free ctx while pressure_write() still holds a reference, triggering UAF when accessing ctx->psi.trigger.

MitigationExtend cgroup_mutex lock scope in pressure_write() to cover all code paths accessing of->priv, and add NULL check for of->priv after acquiring the live kn lock.

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.

NVD · CPE data
Linux KernelOperating system
Affected:>= 5.2, < 6.18.33>= 6.19, < 7.0.10= 7.1

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.

  1. Check installed kernel version
    Run `uname -r` or read `/proc/version` to obtain the running kernel version string
    Affected if The version falls within >= 5.2 and < 6.18.33, OR >= 6.19 and < 7.0.10, OR equals 7.1
  2. Verify cgroup PSI is in use
    Check if any cgroup PSI files exist or are accessed: look for `/sys/fs/cgroup/cpu.pressure`, `/sys/fs/cgroup/memory.pressure`, or `/proc/pressure/` paths
    Affected if These pressure interface files exist and are readable on the system, indicating PSI is enabled
  3. Confirm cgroup1 or cgroup2 controllers are mounted
    Mount information is in `/proc/mounts` or run `mount | grep cgroup` to list cgroup mount points
    Affected if Any cgroup controllers (cpu, memory, io, etc.) are mounted, making the PSI code path active

The system is affected if the running kernel version is within the vulnerable ranges AND cgroup PSI interfaces are accessible on the system.

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 available Upgrade to 6.18.33 / 7.0.10 or later
Fixed in 6.18.337.0.10
Interim mitigation

Extend cgroup_mutex lock scope in pressure_write() to cover all code paths accessing of->priv, and add NULL check for of->priv after acquiring the live kn lock.

Recommended fix High confidence

Linux Kernel 6.18.33 or later for 6.18.x branch; Linux Kernel 7.0.10 or later for 6.19.x/7.0.x/7.1.x branches

  1. 1. Identify the current running kernel version using 'uname -r' or 'cat /proc/version'
  2. 2. For kernels 6.18.x (< 6.18.33): Upgrade to kernel version 6.18.33 or later
  3. 3. For kernels 6.19.x or 7.0.x (< 7.0.10): Upgrade to kernel version 7.0.10 or later
  4. 4. For kernel 7.1: Upgrade to kernel version 7.1.x where x > 0 or the next stable release that includes the fix
  5. 5. After upgrading, verify the fix is applied by checking the kernel release notes or checking the source code for the expanded cgroup_mutex scope in pressure_write() function in kernel/cgroup/cgroup.c
  6. 6. Reboot the system to load the fixed kernel
Caveat Kernel upgrades may require system downtime and should be tested in a staging environment first; ensure compatibility with system hardware and installed kernel modules before production deployment

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

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing12.0 h
  • Review / QA4.0 h
26.0 hours of engineering $4,400
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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-2026-52991 in production — separate from our analysis above.

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