---
id: CVE-2026-53264
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: act_api: use RCU with deferred freeing for action lifecycle

  When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
  race with an assoc…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: act_api: use RCU with deferred freeing for action lifecycle

  When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
  race with an assoc…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 4.14, < 5.10.259'
  - 'linux_kernel >= 5.11, < 5.15.210'
  - 'linux_kernel >= 5.16, < 6.1.176'
  - 'linux_kernel >= 6.2, < 6.6.143'
  - 'linux_kernel >= 6.7, < 6.12.94'
  - 'linux_kernel >= 6.13, < 6.18.36'
  - 'linux_kernel >= 6.19, < 7.0.13'
  - linux_kernel = 7.1
patched:
  - linux_kernel 7.0.13
published: '2026-06-25'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:20:07.843'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53264'
references:
  - url: 'https://git.kernel.org/stable/c/18af5d2ef0c4f65787fd1280c8b23286b9f2a835'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1f1b98fea6b9ea30507d0f2fbff6750292d097e2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5057e1aca011e51ef51498c940ef96f3d3e8a305'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5dd51e09020c65aa53cf128e5e3517cd53b3c113'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8b136f18ac4b2ace5aaad3305b3f8a5d8165a009'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/91d105d2cbe002f9c7b43a6183adedc37e1da1f7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/98b2e40879abf0245be5a5b7af69e0f6ff524ac3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b60e9391142e983fab2be53497aa8f71fdd09cd5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-784472.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://starlabs.sg/blog/2026/07-when-ai-makes-0-days-feel-like-n-days/'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - exploit-available
  - cve.org
epss: 0.00241
epssPercentile: 0.14215
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/HORKimhab/CVE-2026-53264'
  checkedAt: '2026-10-15T03:30:48.758Z'
exploitAvailable: true
ingestedAt: '2026-10-15T03:30:12.912Z'
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-07-29T03:55:26.363824Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_api: use RCU with deferred freeing for action lifecycle

When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.

Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:

 0: mutex_lock() <-- holds the idr lock
 0: rcu_read_lock()
 0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
 0: mutex_unlock() <-- releases the idr lock
 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
 1: idr_remove(idr, index) <-- Action removed from IDR
 1: mutex_unlock() <-- mutex released allowing us to delete the action
 1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory

This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().

Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().

Let's illustrate the new restored code path:

 0: rcu_read_lock()
 1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
 1: idr_remove(idr, index)
 1: mutex_unlock()
 1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
 0: p = idr_find(idr, index)
 0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
 1: rcu_read_unlock() <-- release so freeing can run after grace period

After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.

## Affected

- `linux_kernel >= 4.14, < 5.10.259`
- `linux_kernel >= 5.11, < 5.15.210`
- `linux_kernel >= 5.16, < 6.1.176`
- `linux_kernel >= 6.2, < 6.6.143`
- `linux_kernel >= 6.7, < 6.12.94`
- `linux_kernel >= 6.13, < 6.18.36`
- `linux_kernel >= 6.19, < 7.0.13`
- `linux_kernel = 7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.0.13`