# CVE-2026-53264: net/sched: act_api: use RCU with deferred freeing for action lifecycle > A race condition in the Linux kernel's traffic control API allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 25 Jun 2026 - **Updated:** 15 Oct 2026 - **Also known as:** AZL-90902, BELL-CVE-2026-53264, DEBIAN-CVE-2026-53264, GHSA-vq3g-6qwh-5wj2, RHSA-2026:54482, RHSA-2026:54515, RHSA-2026:55443, ROOT-OS-DEBIAN-11-CVE-2026-53264, ROOT-OS-DEBIAN-12-CVE-2026-53264, ROOT-OS-UBUNTU-2204-CVE-2026-53264, ROOT-OS-UBUNTU-2404-CVE-2026-53264, UBUNTU-CVE-2026-53264 ## What is CVE-2026-53264? CVE-2026-53264 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description 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. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2026-53264? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `bpftool-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:7.0.0-284.187.1.el9_2 | | `kernel-64k-debug-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-devel` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-devel-matched` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-devel` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-devel-matched` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debug-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debug-devel` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debug-devel-matched` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debuginfo-common-aarch64` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debuginfo-common-ppc64le` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debuginfo-common-s390x` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-debuginfo-common-x86_64` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-devel` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-devel-matched` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-doc` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-tools-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-zfcpdump-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-zfcpdump-devel` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-zfcpdump-devel-matched` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `perf` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `perf-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `python3-perf-debuginfo` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `rtla` | Red Hat:rhel_e4s:9.2::appstream | All versions | 0:5.14.0-284.187.1.el9_2 | | `bpftool` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:7.0.0-284.187.1.el9_2 | | `bpftool-debuginfo` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:7.0.0-284.187.1.el9_2 | | `kernel` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-core` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-core` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-debuginfo` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-modules` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-modules-core` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debug-modules-extra` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-debuginfo` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-modules` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | | `kernel-64k-modules-core` | Red Hat:rhel_e4s:9.2::baseos | All versions | 0:5.14.0-284.187.1.el9_2 | Products: Linux kernel. ## How do I fix CVE-2026-53264? Apply the vendor's patch. ## Is CVE-2026-53264 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53264 exists. Public exploit code: - CVE-2026-53264 - Draft or Todo (github_poc): https://github.com/HORKimhab/CVE-2026-53264 - https://github.com/b1nhack/CVE-2026-53264 (github_poc): https://github.com/b1nhack/CVE-2026-53264 ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-53264 and fix it if it is affected. What it is: CVE-2026-53264 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53264 exists. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-53264/ (Markdown: https://insights.sbomify.com/CVE-2026-53264/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53264 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53264 - OSV: https://osv.dev/vulnerability/CVE-2026-53264 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-53264/ Summaries are generated and may contain mistakes; the official description above is the record.