# CVE-2021-3715: Use after free in kernel > Unprivileged local users can escalate privileges via a use-after-free in the Linux kernel Traffic Control subsystem. - **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:** 2 Mar 2022 - **Updated:** 3 Aug 2024 - **Also known as:** A-223966861, DEBIAN-CVE-2021-3715, GHSA-gcff-f9p7-hmfg, OESA-2021-1341, PUB-A-223966861, RHSA-2021:3438, RHSA-2021:3439, RHSA-2021:3441, UBUNTU-CVE-2021-3715 ## What is CVE-2021-3715? CVE-2021-3715 is a high-severity use after free vulnerability in Linux kernel, published on 2 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description A flaw was found in the "Routing decision" classifier in the Linux kernel's Traffic Control networking subsystem in the way it handled changing of classification filters, leading to a use-after-free condition. This flaw allows unprivileged local users to escalate their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2021-3715? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `bpftool` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `bpftool-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-abi-whitelists` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-x86_64` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-doc` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools-libs` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools-libs-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `perf` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `perf-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `python-perf` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `python-perf-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.10.0-1160.42.2.el7 | | `bpftool-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-x86_64` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-tools-libs-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `perf-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `python-perf-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.10.0-1160.42.2.el7 | | `bpftool` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `bpftool-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-abi-whitelists` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-bootwrapper` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debug-devel` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-ppc64` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-ppc64le` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-s390x` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | | `kernel-debuginfo-common-x86_64` | Red Hat:enterprise_linux:7::server | All versions | 0:3.10.0-1160.42.2.el7 | Products: Linux kernel. ## How do I fix CVE-2021-3715? Apply the vendor's patch. ## Is CVE-2021-3715 being exploited? There is no known exploitation of CVE-2021-3715 in the wild and no public exploit code. ## 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-2021-3715 and fix it if it is affected. What it is: CVE-2021-3715 is a high-severity use after free vulnerability in Linux kernel, published on 2 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-3715 in the wild and no public exploit code. 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-2021-3715/ (Markdown: https://insights.sbomify.com/CVE-2021-3715/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3715 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3715 - OSV: https://osv.dev/vulnerability/CVE-2021-3715 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-3715/ Summaries are generated and may contain mistakes; the official description above is the record.