CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE

A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space

8.3 HIGHEPSS 78.68%⚡ Known Exploited (CISA KEV)NVD: Analyzed

Last updated: 2026-10-13 18:25 UTC

OverviewCVSS details

8.3HIGHCVSS 3.1

Score source: Google (CNA)
NVD status: Analyzed
Published: Jul 7, 2021
Assigner: Google

Affected

Linux Kernel

Versions: 2.6.19-rc1 before unspecified
Fixed in: unspecified

Exploitation

Public exploit: Yes · 5 references
CISA KEV: Listed · Oct 6, 2025
KEV due date: Oct 27, 2025
Ransomware use: Unknown
SSVC: Exploitation active · Automatable no · Impact total

EPSS · FIRST, scored Nov 7

78.68%chance of exploitation in 30 days

Higher than 99.59% of CVEs

CVSS 3.1 · Google (CNA)

8.3High

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Attack vector: Adjacent
Attack complexity: High
Privileges required: None
User interaction: None
Scope: Changed
Confidentiality impact: High
Integrity impact: High
Availability impact: High

CVSS 3.1 · NVD

7.8High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

CVSS 2.0 · NVD

4.6Medium

AV:L/AC:L/Au:N/C:P/I:P/A:P

Attack vector: Local
Attack complexity: Low
Authentication: None
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

NVD status: Analyzed

Overview Affected Products References

NVD CVE.org

Overview

Severity

Score	Severity	Version	Vector String
8.3	HIGH	3.1Google (CNA)	CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
7.8	HIGH	3.1NVD	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6	MEDIUM	2.0NVD	AV:L/AC:L/Au:N/C:P/I:P/A:P

CISA required action

⚡ Known exploited · remediation due Oct 27, 2025

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Details

CVE ID: CVE-2021-22555
Status: Analyzed
Assigner (CNA): Google
Published: Jul 7, 2021
Last modified: 2026-10-13 18:25 UTC
Weaknesses: CWE-787 · Out-of-bounds Write

Sources

Refreshed hourly from the sources above. Last fetched 2026-11-08 11:18 UTC.