Is CVE-2021-22555 in the CISA KEV catalog?

Yes. CVE-2021-22555 is on the CISA Known Exploited Vulnerabilities list, added 2025-10-06.

What is the CVSS severity of CVE-2021-22555?

CVE-2021-22555 has a CVSS v3 base score of 8.3 (HIGH).

What is the EPSS score for CVE-2021-22555?

CVE-2021-22555 has an EPSS score of 78.68% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-22555?

Upgrade linux on debian 11 to 5.10.38-1 or later. Fixes are available for 76 affected products.

CVE & CISA-KEV Catalog

CVE-2021-22555

HIGHCISA KEVEPSS 100th pctl

8.3

CVSS v3

NVD

Description

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

CWE-787Out-of-bounds Write

How to fix

Remediation Available

linuxDebian

Fixed in:5.10.38-1CVE-2021-22555

kernelRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernelRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-abi-whitelistsRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-abi-whitelistsRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debugRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debugRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debug-debuginfoRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debug-debuginfoRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debug-develRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debug-develRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfoRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfoRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-i686Red Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-i686Rocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-s390xRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-s390xRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-x86_64Rocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-debuginfo-common-x86_64Red Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-develRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-develRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-docRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-docRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-firmwareRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-firmwareRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdumpRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdumpRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdump-debuginfoRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdump-debuginfoRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdump-develRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

kernel-kdump-develRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

perfRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

perfRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

perf-debuginfoRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

perf-debuginfoRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

python-perfRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

python-perfRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

python-perf-debuginfoRed Hat / RHEL

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

python-perf-debuginfoRocky

Fixed in:0:2.6.32-754.58.1.el6RHSA-2025:17733

awsUbuntu

Fixed in:4.4.0-1098LSN-0083-1

Fixed in:4.15.0-1054LSN-0083-1

Fixed in:5.4.0-1009LSN-0083-1

azureUbuntu

Fixed in:4.15.0-1063LSN-0083-1

Fixed in:5.4.0-1010LSN-0083-1

gcpUbuntu

Fixed in:5.4.0-1009LSN-0080-1

Fixed in:5.4.0-1009LSN-0081-1

Fixed in:5.4.0-1009LSN-0083-1

generic-4.15Ubuntu

Fixed in:4.15.0-143LSN-0083-1

Fixed in:4.15.0-69LSN-0081-1

Fixed in:4.15.0-69LSN-0080-1

Fixed in:4.15.0-69LSN-0083-1

Fixed in:4.15.0-69LSN-0081-1

generic-4.4Ubuntu

Fixed in:4.4.0-168LSN-0080-1

Fixed in:4.4.0-168LSN-0081-1

Fixed in:4.4.0-211LSN-0083-1

Fixed in:4.4.0-168LSN-0080-1

Fixed in:4.4.0-211LSN-0081-1

generic-5.4Ubuntu

Fixed in:5.4.0-26LSN-0080-1

Fixed in:5.4.0-26LSN-0081-1

Fixed in:5.4.0-26LSN-0083-1

Fixed in:5.4.0-26LSN-0080-1

Fixed in:5.4.0-26LSN-0081-1

gkeUbuntu

Fixed in:5.4.0-1033LSN-0081-1

Fixed in:5.4.0-1033LSN-0080-1

Fixed in:5.4.0-1033LSN-0083-1

gke-4.15Ubuntu

Fixed in:4.15.0-1076LSN-0081-1

Fixed in:4.15.0-1076LSN-0083-1

Fixed in:4.15.0-1076LSN-0080-1

gke-5.4Ubuntu

Fixed in:5.4.0-1009LSN-0081-1

Fixed in:5.4.0-1009LSN-0083-1

Fixed in:5.4.0-1009LSN-0080-1

gkeopUbuntu

Fixed in:5.4.0-1009LSN-0080-1

Fixed in:5.4.0-1009LSN-0081-1

Fixed in:5.4.0-1009LSN-0083-1

gkeop-5.4Ubuntu

Fixed in:5.4.0-1007LSN-0080-1

Fixed in:5.4.0-1007LSN-0081-1

Fixed in:5.4.0-1007LSN-0083-1

linuxUbuntu

Fixed in:3.13.0-187.238USN-5039-1

Fixed in:4.4.0-213.245USN-5039-1

linux-awsUbuntu

Fixed in:4.4.0-1095.100USN-5039-1

Fixed in:4.4.0-1131.145USN-5039-1

linux-image-3.13.0-187-genericUbuntu

Fixed in:3.13.0-187.238USN-5039-1

linux-image-3.13.0-187-generic-lpaeUbuntu

Fixed in:3.13.0-187.238USN-5039-1

linux-image-3.13.0-187-lowlatencyUbuntu

Fixed in:3.13.0-187.238USN-5039-1

linux-image-4.4.0-1095-awsUbuntu

Fixed in:4.4.0-1095.100USN-5039-1

linux-image-4.4.0-1096-kvmUbuntu

Fixed in:4.4.0-1096.105USN-5039-1

linux-image-4.4.0-1131-awsUbuntu

Fixed in:4.4.0-1131.145USN-5039-1

linux-image-4.4.0-213-genericUbuntu

Fixed in:4.4.0-213.245~14.04.1USN-5039-1

Fixed in:4.4.0-213.245USN-5039-1

linux-image-4.4.0-213-lowlatencyUbuntu

Fixed in:4.4.0-213.245~14.04.1USN-5039-1

Fixed in:4.4.0-213.245USN-5039-1

linux-image-awsUbuntu

Fixed in:4.4.0.1095.93USN-5039-1

Fixed in:4.4.0.1131.136USN-5039-1

linux-image-genericUbuntu

Fixed in:3.13.0.187.196USN-5039-1

Fixed in:4.4.0.213.220USN-5039-1

linux-image-generic-lpaeUbuntu

Fixed in:3.13.0.187.196USN-5039-1

linux-image-generic-lts-xenialUbuntu

Fixed in:4.4.0.213.186USN-5039-1

linux-image-kvmUbuntu

Fixed in:4.4.0.1096.94USN-5039-1

linux-image-lowlatencyUbuntu

Fixed in:3.13.0.187.196USN-5039-1

Fixed in:4.4.0.213.220USN-5039-1

linux-image-lowlatency-lts-xenialUbuntu

Fixed in:4.4.0.213.186USN-5039-1

linux-image-serverUbuntu

Fixed in:3.13.0.187.196USN-5039-1

linux-image-virtualUbuntu

Fixed in:3.13.0.187.196USN-5039-1

Fixed in:4.4.0.213.220USN-5039-1

linux-image-virtual-lts-xenialUbuntu

Fixed in:4.4.0.213.186USN-5039-1

linux-kvmUbuntu

Fixed in:4.4.0-1096.105USN-5039-1

linux-lts-xenialUbuntu

Fixed in:4.4.0-213.245~14.04.1USN-5039-1

lowlatency-4.15Ubuntu

Fixed in:4.15.0-69LSN-0080-1

Fixed in:4.15.0-69LSN-0081-1

Fixed in:4.15.0-143LSN-0083-1

Fixed in:4.15.0-69LSN-0083-1

Fixed in:4.15.0-69LSN-0080-1

Fixed in:4.15.0-69LSN-0081-1

lowlatency-4.4Ubuntu

Fixed in:4.4.0-168LSN-0080-1

Fixed in:4.4.0-168LSN-0081-1

Fixed in:4.4.0-211LSN-0081-1

Fixed in:4.4.0-211LSN-0083-1

Fixed in:4.4.0-168LSN-0080-1

lowlatency-5.4Ubuntu

Fixed in:5.4.0-26LSN-0081-1

Fixed in:5.4.0-26LSN-0080-1

Fixed in:5.4.0-26LSN-0081-1

Fixed in:5.4.0-26LSN-0083-1

oemUbuntu

Fixed in:4.15.0-1063LSN-0081-1

Fixed in:4.15.0-1063LSN-0080-1

Fixed in:4.15.0-1063LSN-0083-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorAdjacent

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

78.68%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Linux Kernel Heap Out-of-Bounds Write Vulnerability

Linux Kernel contains a heap out-of-bounds write vulnerability that could allow an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space.

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

Remediation due: 2025-10-27

References

Patch2

Exploit5

Third-Party Advisory2

Government Resource1

cisa.gov

Related Vulnerabilities

Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2023-4863	High	8.8	100%	KEV	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-10-27.