CVE-2021-4154 Use after free in kernel

What is CVE-2021-4154?

CVE-2021-4154 is a high-severity use after free vulnerability in Linux kernel, published on 4 Feb 2022. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

A use-after-free flaw was found in cgroup1_parse_param in kernel/cgroup/cgroup-v1.c in the Linux kernel's cgroup v1 parser. A local attacker with a user privilege could cause a privilege escalation by exploiting the fsconfig syscall parameter leading to a container breakout and a denial of service on the system.

Weakness: CWE-416

Which versions are affected by CVE-2021-4154?

It affects 4 products.

Products include Linux kernel, Netapp Hci Baseboard Management Controller, Redhat Enterprise Linux, Redhat Virtualization.

How do I fix CVE-2021-4154?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-4154 being exploited?

There is no known exploitation of CVE-2021-4154 in the wild and no public exploit code.

Public exploit code: 2 proofs of concept on GitHub.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as A-218836280, ASB-A-218836280, DEBIAN-CVE-2021-4154, GHSA-qvm5-4fh7-hcfx, UBUNTU-CVE-2021-4154.