{"id":"CVE-2021-4001","title":"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","summary":"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) c…","severity":"medium","cvss":4.1,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N","cwe":["CWE-367","CWE-367"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel <= 5.15","linux_kernel = 5.16"],"published":"2022-01-21","updated":"2026-10-08","sourceUpdated":"2026-10-08T21:17:42.587","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2021-4001","references":[{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2025645","label":"secalert@redhat.com"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=353050be4c19e102178ccc05988101887c25ae53","label":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2025645","label":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=353050be4c19e102178ccc05988101887c25ae53","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd"],"epss":0.00186,"epssPercentile":0.07549,"ingestedAt":"2026-10-08T22:11:53.744Z","slug":"CVE-2021-4001","body":"## Overview\n\nA 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.\n\n## Affected\n\n- `linux_kernel <= 5.15`\n- `linux_kernel = 5.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":23,"depthScoreParts":{"impact":22.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}