CVE-2021-4001 Race condition in kernel

What is CVE-2021-4001?

CVE-2021-4001 is a medium-severity vulnerability in Linux kernel, published on 21 Jan 2022. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

A race condition was found in the Linux kernel's ebpf verifier between bpf_map_update_elem and bpf_map_freeze due to a missing lock in kernel/bpf/syscall.c. In this flaw, a local user with a special privilege (cap_sys_admin or cap_bpf) can modify the frozen mapped address space. This flaw affects kernel versions prior to 5.16 rc2.

Weakness: CWE-367

Which versions are affected by CVE-2021-4001?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2021-4001?

Apply the vendor's patch.

Is CVE-2021-4001 being exploited?

There is no known exploitation of CVE-2021-4001 in the wild and no public exploit code.

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 DEBIAN-CVE-2021-4001, GHSA-q6qm-pxcx-gj5h, UBUNTU-CVE-2021-4001.