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-2021-3520

CVE-2021-3520CRITICAL

n/a lz4 — There's a flaw in lz4.

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  H    9.8   .0340   88.7     —

AFFECTED
  Product  Versions     Fixed
  lz4      lz4-1.8.3 –  —

TIMELINE
  Apr 28  Reserved by redhat
  Jun 2   Published (CNA: redhat)
  Oct 8   ENRICHED — CVE-2021-3520 (lz4). Received CVSS 9.8 and CPE data from NVD.

CWE-190, CWE-787 · CNA: redhat · CVSS v3.1 · 6 references · NVD status: Modified

Description

There's a flaw in lz4. An attacker who submits a crafted file to an application linked with lz4 may be able to trigger an integer overflow, leading to calling of memmove() on a negative size argument, causing an out-of-bounds write and/or a crash. The greatest impact of this flaw is to availability, with some potential impact to confidentiality and integrity as well.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
April 28, 2021	Reserved	Reserved by redhat
June 2, 2021	Published	Published (CNA: redhat)
October 8, 2026	ENRICHED	ENRICHED — CVE-2021-3520 (lz4). Received CVSS 9.8 and CPE data from NVD.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
n/a	lz4	—	lz4-1.8.3	—

Weaknesses

CWE-190 · CWE-787

References (6)

https://bugzilla.redhat.com/show_bug.cgi?id=1954559 [Issue Tracking, Patch, Third Party Advisory]
https://cert-portal.siemens.com/productcert/html/ssa-398330.html
https://security.netapp.com/advisory/ntap-20211104-0005/ [Third Party Advisory]
https://www.oracle.com//security-alerts/cpujul2021.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuapr2022.html [Patch, Third Party Advisory]
https://www.oracle.com/security-alerts/cpuoct2021.html [Patch, Third Party Advisory]

Authoritative record: CVE-2021-3520 at cve.org

Weaknesses: CWE-190 · CWE-787

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-3520 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.