Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-4001

CVE-2021-4001MEDIUM

n/a kernel — 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 ke…

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   H   H   N  U  N  H  N    4.1   .0019    7.7     —

AFFECTED
  Product  Versions           Fixed
  kernel   kernel 5.16 rc2 –  —

TIMELINE
  Nov 22  Reserved by redhat
  Jan 21  Published (CNA: redhat)
  Oct 8   ENRICHED — CVE-2021-4001 (kernel). Received CVSS 4.1 and CPE data from NVD.

CWE-367 · CNA: redhat · CVSS v3.1 · 2 references · NVD status: Modified

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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
November 22, 2021	Reserved	Reserved by redhat
January 21, 2022	Published	Published (CNA: redhat)
October 8, 2026	ENRICHED	ENRICHED — CVE-2021-4001 (kernel). Received CVSS 4.1 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
n/a	kernel	—	kernel 5.16 rc2	—

Weaknesses

CWE-367

References (2)

https://bugzilla.redhat.com/show_bug.cgi?id=2025645 [Issue Tracking, Patch, Third Party Advisory]
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=353050be4c19e102178ccc05988101887c25ae53 [Patch, Third Party Advisory]

Authoritative record: CVE-2021-4001 at cve.org

Weaknesses: CWE-367

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-4001 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.