Public proof of conceptFix available

CVE-2021-4204

Q: Is CVE-2021-4204 actively exploited?

Active exploitation of CVE-2021-4204 has not been confirmed. Its EPSS score was 1.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-4204?

CVE-2021-4204 has a CVSS v3 base score of 7.1 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H.

A public proof of concept exists; no exploitation attested.

Published2022-08-24
Fixed in5.8.0
WeaknessCWE-119 · CWE-20

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

An out-of-bounds (OOB) memory access flaw was found in the Linux kernel's eBPF due to an Improper Input Validation. This flaw allows a local attacker with a special privilege to crash the system or leak internal information.

Timeline

dates in UTC

2022-08-2416:15CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-4204?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-4204?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Linux linux kernel

Branch	Affected	Fixed in	Source
5.8	< 5.8.0	5.8.0	NVD
5.8	= 5.8.0	no fix published	NVD

Debian debian linux

Branch	Affected	Fixed in	Source
11.0	= 11.0	no fix published	NVD

Netapp h300s firmwareversion to verify

Branch	Affected	Fixed in	Source
—	all versions	no fix published	NVD

5 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Linux linux kernel to 5.8.0

Advisories and patches

access.redhat.comMitigation
www.openwall.comPatch

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedtr3ee/CVE-2021-4204

Sources

NVDCVSS 3.17.1read 2026-10-23
CNAweakness (CWE)CWE-20read 2026-10-23
NVDweakness (CWE)CWE-119read 2026-10-23
FIRST EPSSEPSS score1.2 %2026-10-22
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Published: 2022-08-24
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-4204?

Is CVE-2021-4204 actively exploited?

Active exploitation of CVE-2021-4204 has not been confirmed. Its EPSS score was 1.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-4204?

CVE-2021-4204 has a CVSS v3 base score of 7.1 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H.

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