# CVE-2021-22555: Linux Kernel Heap Out-of-Bounds Write > A heap out-of-bounds write in the Linux kernel netfilter allows attackers to gain privileges or cause denial of service via user namespaces. - **Severity:** High 8.3 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`) - **Exploited in the wild:** Yes, since 6 Oct 2025 (CISA KEV) - **Login needed:** Not needed - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 Jul 2021 - **Updated:** 30 Dec 2025 - **Also known as:** A-184847809, CLSA-2021-1632261894, CLSA-2021-1632261912, DEBIAN-CVE-2021-22555, LSN-0080-1, PUB-A-184847809, RHSA-2025:17733, UBUNTU-CVE-2021-22555, USN-5039-1 ## What is CVE-2021-22555? CVE-2021-22555 is a high-severity memory corruption vulnerability in Broadcom Fabric Operating System, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space Weakness: CWE-787 (Out-of-bounds Write) ## Which versions are affected by CVE-2021-22555? It affects 21 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `kernel` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-abi-whitelists` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debug` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debug-debuginfo` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debug-devel` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debuginfo` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debuginfo-common-i686` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debuginfo-common-s390x` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-debuginfo-common-x86_64` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-devel` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-doc` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-firmware` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-kdump` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-kdump-debuginfo` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `kernel-kdump-devel` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `perf` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `perf-debuginfo` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `python-perf` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | | `python-perf-debuginfo` | Red Hat:rhel_els:6 | All versions | 0:2.6.32-754.58.1.el6 | Products: Broadcom Fabric Operating System, Linux kernel, Netapp Aff 500f Firmware, Netapp Aff A250 Firmware, Netapp Aff A400 Firmware, Netapp C250 Firmware, Netapp C400 Firmware, Netapp Cloud Backup, Netapp Fas 8300 Firmware, Netapp Fas 8700 Firmware, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H610c Firmware, Netapp H610s Firmware, Netapp H615c Firmware, Netapp H700s Firmware, Netapp Hci Management Node, Netapp Solidfire and 1 more. ## How do I fix CVE-2021-22555? Apply the vendor's patch. US federal agencies must fix it by 27 Oct 2025. ## Is CVE-2021-22555 being exploited? Yes. Attackers have exploited CVE-2021-22555 in the wild since at least 6 Oct 2025. Public exploit code: - CVE-2021-22555 exploit rewritten with pipe primitive (github_poc): https://github.com/veritas501/CVE-2021-22555-PipeVersion - CVE-2021-22555 Exploit (github_poc): https://github.com/xyjl-ly/CVE-2021-22555-Exploit - https://github.com/cgwalters/container-cve-2021-22555 (github_poc): https://github.com/cgwalters/container-cve-2021-22555 - This repo hosts TUKRU's Linux Privilege Escalation exploit (CVE-2021-22555). It demonstrates gaining root privileges via a vulnerability. Tested on Ubuntu 5.8.0-48-generic and COS 5.4.89+. Use responsibly and ethically. (github_poc): https://github.com/tukru/CVE-2021-22555 - https://github.com/JoneyJunior/cve-2021-22555 (github_poc): https://github.com/JoneyJunior/cve-2021-22555 - https://github.com/daletoniris/CVE-2021-22555-esc-priv (github_poc): https://github.com/daletoniris/CVE-2021-22555-esc-priv ## Other vulnerabilities in Broadcom Fabric Operating System - [CVE-2025-1976](https://insights.sbomify.com/CVE-2025-1976/): Broadcom Brocade Fabric OS Code Injection (high 8.6, exploited in the wild) - [CVE-2022-33186](https://insights.sbomify.com/CVE-2022-33186/): Command injection in Brocade Fabric OS (critical 9.8) - [CVE-2021-27797](https://insights.sbomify.com/CVE-2021-27797/): Hardcoded credentials in Brocade Fabric OS (critical 9.8) - [CVE-2020-15371](https://insights.sbomify.com/CVE-2020-15371/): Code injection in Brocade Fabric OS (critical 9.8) - [CVE-2020-15373](https://insights.sbomify.com/CVE-2020-15373/): Memory corruption in Brocade Fabric OS (critical 9.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-22555 and fix it if it is affected. What it is: CVE-2021-22555 is a high-severity memory corruption vulnerability in Broadcom Fabric Operating System, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: Yes. Attackers have exploited CVE-2021-22555 in the wild since at least 6 Oct 2025. Affected product: Broadcom Fabric Operating System. 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-2021-22555/ (Markdown: https://insights.sbomify.com/CVE-2021-22555/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-22555 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-22555 - OSV: https://osv.dev/vulnerability/CVE-2021-22555 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-22555/ Summaries are generated and may contain mistakes; the official description above is the record.