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.
- Exploited in the wild
- Since 6 Oct 2025
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2021-22555?
It affects 21 products.
Linux distribution packages (19)
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 include Broadcom Fabric Operating System, Linux kernel, Netapp Aff 500f Firmware, Netapp Aff A250 Firmware, Netapp Aff A400 Firmware, Netapp C250 Firmware and 15 more.
How do I fix CVE-2021-22555?
Apply the vendor's patch. US federal agencies must fix it by 27 Oct 2025.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
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: 1 Metasploit module, 1 Exploit-DB entry and 13 proofs of concept on GitHub.
Other vulnerabilities in Broadcom Fabric Operating System
Sources
Also known as A-184847809, CLSA-2021-1632261894, CLSA-2021-1632261912, DEBIAN-CVE-2021-22555, LSN-0080-1, PUB-A-184847809 and 3 more.