Vulnerability · CVE-2021-3520
There's a flaw in lz4.
Published Jun 2, 2021 · catalog updated Oct 14, 2026 · lz4 project
Check if you run it
No confirmed exploitation is on record for CVE-2021-3520. EPSS is 3.40%. Act only if a listed version of lz4 project is installed.
Gaps on this record
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Critical9.8
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 3.40%
- Remediation
- Advisory link
- Affected products
- cpe lz4 project/lz4 · cpe netapp/active iq unified manager · cpe netapp/cloud backup · cpe netapp/ontap select deploy administration utility · cpe oracle/communications cloud native core policy · cpe oracle/zfs storage appliance kit
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.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe lz4 project/lz4version unspecified
- cpe netapp/active iq unified managerversion unspecified
- cpe netapp/cloud backupversion unspecified
- cpe netapp/ontap select deploy administration utilityversion unspecified
- cpe oracle/communications cloud native core policy1.14.0
- cpe oracle/zfs storage appliance kit8.8
- cpe splunk/universal forwarderversion unspecified
How to fix CVE-2021-3520
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2021-3520. EPSS is 3.40%. Act only if a listed version of lz4 project is installed.
Which versions are affected?
Compare what you have installed with oracle/communications cloud native core policy 1.14.0; oracle/zfs storage appliance kit 8.8. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-190: Integer Overflow; CWE-787: Out-of-bounds Write. EPSS 3.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Jun 2, 2021 · NIST NVD
Detected
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.
Oct 14, 2026 · NIST NVD
Updated
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.
Sources
- CVE.orgVulnerability recordCVE-2021-3520
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2021-3520
30-day exploitation probability 3.4%
first.org - NIST NVDVulnerability recordCVE-2021-3520
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
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 16, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.