`CVE-2021-22555`

Severity	8.3 High CVSS 3.1 3 scores
Weakness	Out-of-bounds write (CWE-787)
Published	7 Jul 2021
Updated	13 Oct 2026

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

Exploitation status

Exploited

Confirmed real-world exploitation.

CISA KEV listed Confirmed exploitation in the wild. Added 2025-10-06 · remediation due 2025-10-27 · ransomware use: unknown
VulnCheck KEV listed Exploitation reported in the wild. 8 citations · 15 exploits · earliest 2024-03-18.
CISA Vulnrichment exploitation: active CISA records active exploitation. Automatable: no, technical impact: total.
Indexed PoC 11 indexed Published artifacts you can open, in Exploit-DB, GitHub PoC, Metasploit; first seen 2021-07-15.
EPSS 79% chance in 30 days A model's forecast, not a report of exploitation. Higher than 99.6% of all scored CVEs.

VulnCheck KEV

Exploitation evidence from VulnCheck Known Exploited Vulnerabilities (VulnCheck KEV), used under VulnCheck's community terms. View CVE-2021-22555 in VulnCheck (free account), which lists 3 more citations and 10 more exploit references not shown here.

Evidence	Source	Detail	Date
Reported exploitation	trendmicro.com	/en_us/research/24/c/earth-krahang.html	2024-03-18
Reported exploitation	securelist.com	/vulnerabilities-and-exploits-in-q2-2025/117333	2025-08-27
Reported exploitation	cisa.gov	/sites/default/files/feeds/known_exploited_vulnerabilities.json	2025-10-06
Reported exploitation	securelist.com	/vulnerabilities-and-exploits-in-q3-2025/118197	2025-12-03
Reported exploitation	loginsoft.com	/reports/annually/vulnerability-intelligence-report-2025	2026-01-20
Exploit reference	VulnCheck XDB 8ef3da70ba6c	Exploit type: local	2021-03-30
Exploit reference	VulnCheck XDB b14c9c8213f1	Exploit type: local	2021-07-16
Exploit reference	VulnCheck XDB e7c8672f5830	Exploit type: local	2021-07-16
Exploit reference	VulnCheck XDB 82616da9904f	Exploit type: local	2021-09-03
Exploit reference	VulnCheck XDB 927960b6eeeb	Exploit type: local	2021-11-19

Evidence

Source

Detail

Date

Reported exploitation

trendmicro.com

/en_us/research/24/c/earth-krahang.html

2024-03-18

Reported exploitation

securelist.com

/vulnerabilities-and-exploits-in-q2-2025/117333

2025-08-27

Reported exploitation

cisa.gov

/sites/default/files/feeds/known_exploited_vulnerabilities.json

2025-10-06

Reported exploitation

securelist.com

/vulnerabilities-and-exploits-in-q3-2025/118197

2025-12-03

Reported exploitation

loginsoft.com

/reports/annually/vulnerability-intelligence-report-2025

2026-01-20

Exploit reference

VulnCheck XDB 8ef3da70ba6c

Exploit type: local

2021-03-30

Exploit reference

VulnCheck XDB b14c9c8213f1

Exploit type: local

2021-07-16

Exploit reference

VulnCheck XDB e7c8672f5830

Exploit type: local

2021-07-16

Exploit reference

VulnCheck XDB 82616da9904f

Exploit type: local

2021-09-03

Exploit reference

VulnCheck XDB 927960b6eeeb

Exploit type: local

2021-11-19

6 of these are GitHub repositories with fewer than 5 stars. They are listed for reference and don't count toward the exploitation status above.

Index	Artifact	Stars	First seen
GitHub PoC	CVE-2021-22555 exploit rewritten with pipe primitive	40	2022-04-05
Exploit-DB	Linux Kernel 2.6.19 < 5.9 - 'Netfilter Local Privilege Escalation		2021-07-15
Metasploit	Netfilter x_tables Heap OOB Write Privilege Escalation (great rank)
GitHub PoC	CVE-2021-22555 Exploit	14	2021-07-16
GitHub PoC	cgwalters/container-cve-2021-22555	4	2021-07-16
GitHub PoC	This repo hosts TUKRU's Linux Privilege Escalation exploit (CVE-2021-22555). It demonstrates gaining root privileges via a vulnerability. Tested on Ubuntu 5.8.0-48-generic and COS 5.4.89+. Use responsibly and ethically.	3	2023-08-05
GitHub PoC	Spydomain/CVE-2021-22555-Poc	1	2026-02-02
GitHub PoC	Script of Network Security Project - Attack on CVE-2021-22555	1	2023-05-10
GitHub PoC	daletoniris/CVE-2021-22555-esc-priv	1	2021-10-01
GitHub PoC	JoneyJunior/cve-2021-22555	1	2021-07-15

Waratek protection

Outside Waratek scope

A Java vulnerability, but not one Waratek protects. It affects only Java on a user's desktop (applets, Web Start, JavaFX, the installer), sits in a product the Waratek agent can't be installed into, or is in a package we don't expect in business applications. The decision below says which.

Protection none
Action not pursued none
Review human Researcher
Record active

Decided by	Manual classification of this CVE in the legacy dataset
Finding	A manual classification set this CVE's status to Outside Waratek scope, but the CVE names a tracked product.

Decided by

Manual classification of this CVE in the legacy dataset

Finding

A manual classification set this CVE's status to Outside Waratek scope, but the CVE names a tracked product.

CVSS

8.3 HIGH v3.1 CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H 3 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 8.3 HIGH CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H cve-coordination@google.com Secondary published

CVSS 3.1 7.8 HIGH CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H NVD Primary

CVSS 2.0 4.6 none AV:L/AC:L/Au:N/C:P/I:P/A:P NVD Primary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	8.3	HIGH	`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`	cve-coordination@google.com	Secondary	published
CVSS 3.1	7.8	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`	NVD	Primary
CVSS 2.0	4.6	none	`AV:L/AC:L/Au:N/C:P/I:P/A:P`	NVD	Primary

Affected software and releases

Oracle advisories

Advisory	Type	Quarter	Products Oracle names in its risk matrix
Oracle Critical Patch Update July 2026 ↗	CPU	2026-Q3	Oracle JD Edwards / E1 Foundation (swift) (9.2)

Advisory

Type

Quarter

Products Oracle names in its risk matrix

Oracle Critical Patch Update July 2026 ↗

CPU

2026-Q3

Oracle JD Edwards / E1 Foundation (swift) (9.2)

Oracle components and versions

Family	Component	Versions, as Oracle lists them	Read as
Oracle JD Edwards	E1 Foundation (swift)	9.2	9.2

Family

Component

Versions, as Oracle lists them

Read as

Oracle JD Edwards

E1 Foundation (swift)

9.2

Products and versions

21 products, 27 version entries

Source	Vendor	Product	Scheme	Affected versions
nvd	broadcom	fabric operating system	generic	any version
nvd	linux	linux kernel	generic	≥ 2.6.19 and ＜ 4.4.267 · ≥ 4.5 and ＜ 4.9.267 · ≥ 4.10 and ＜ 4.14.231 · ≥ 4.15 and ＜ 4.19.188 · ≥ 4.20 and ＜ 5.4.113 · ≥ 5.5 and ＜ 5.10.31 · ≥ 5.11 and ＜ 5.12
nvd	netapp	aff 500f firmware	generic	any version
nvd	netapp	aff a250 firmware	generic	any version
nvd	netapp	aff a400 firmware	generic	any version
nvd	netapp	c250 firmware	generic	any version
nvd	netapp	c400 firmware	generic	any version
nvd	netapp	cloud backup	generic	any version
nvd	netapp	fas 8300 firmware	generic	any version
nvd	netapp	fas 8700 firmware	generic	any version
nvd	netapp	h300s firmware	generic	any version
nvd	netapp	h410c firmware	generic	any version
nvd	netapp	h410s firmware	generic	any version
nvd	netapp	h500s firmware	generic	any version
nvd	netapp	h610c firmware	generic	any version
nvd	netapp	h610s firmware	generic	any version
nvd	netapp	h615c firmware	generic	any version
nvd	netapp	h700s firmware	generic	any version
nvd	netapp	hci management node	generic	any version
nvd	netapp	solidfire	generic	any version
nvd	netapp	solidfire baseboard management controller	generic	any version

Source

Vendor

Product

Scheme

Affected versions

nvd

broadcom

fabric operating system

generic

any version

nvd

linux

linux kernel

generic

≥ 2.6.19 and ＜ 4.4.267 · ≥ 4.5 and ＜ 4.9.267 · ≥ 4.10 and ＜ 4.14.231 · ≥ 4.15 and ＜ 4.19.188 · ≥ 4.20 and ＜ 5.4.113 · ≥ 5.5 and ＜ 5.10.31 · ≥ 5.11 and ＜ 5.12

nvd

netapp

aff 500f firmware

generic

any version

nvd

netapp

aff a250 firmware

generic

any version

nvd

netapp

aff a400 firmware

generic

any version

nvd

netapp

c250 firmware

generic

any version

nvd

netapp

c400 firmware

generic

any version

nvd

netapp

cloud backup

generic

any version

nvd

netapp

fas 8300 firmware

generic

any version

nvd

netapp

fas 8700 firmware

generic

any version

nvd

netapp

h300s firmware

generic

any version

nvd

netapp

h410c firmware

generic

any version

nvd

netapp

h410s firmware

generic

any version

nvd

netapp

h500s firmware

generic

any version

nvd

netapp

h610c firmware

generic

any version

nvd

netapp

h610s firmware

generic

any version

nvd

netapp

h615c firmware

generic

any version

nvd

netapp

h700s firmware

generic

any version

nvd

netapp

hci management node

generic

any version

nvd

netapp

solidfire

generic

any version

nvd

netapp

solidfire baseboard management controller

generic

any version

References

URL	Tags
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d
https://security.netapp.com/advisory/ntap-20210805-0010/
https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528
http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html	Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html	Exploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html	Exploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html	Exploit, Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html	Exploit, Third Party Advisory, VDB Entry
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22555	US Government Resource

URL

Timeline

Published	2021-07-07	By the CVE Program.
VulnCheck KEV: earliest evidence	2024-03-18	Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.
Added to CISA KEV	2025-10-06	Listed in CISA's Known Exploited Vulnerabilities catalog.
VulnCheck KEV: latest evidence	2026-08-26	Date of the newest report, exploit reference or honeypot sighting in VulnCheck KEV's record.
NVD record modified	2026-10-13	NVD's own last-modified date for this record.

Published

2021-07-07

By the CVE Program.

VulnCheck KEV: earliest evidence

2024-03-18

Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.

Added to CISA KEV

2025-10-06

Listed in CISA's Known Exploited Vulnerabilities catalog.

VulnCheck KEV: latest evidence

2026-08-26

Date of the newest report, exploit reference or honeypot sighting in VulnCheck KEV's record.

NVD record modified

2026-10-13

NVD's own last-modified date for this record.

How VRT decided (5 of 24 rules ran)

5 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification decided it matched Outside Waratek scope Found in legacy manual classifications

6 non-java-upstream not reached A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component not reached The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side not reached Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven not reached An OSV.dev record of this CVE affecting a package published to Maven Central. When every such package is one business applications do not use (Minecraft mods and launchers, Fastjson) and no tracked product is named by CPE, it settles the CVE as Outside Waratek scope instead

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint not reached A reference pointing at the upstream fix: a commit, a PR, a Red Hat bug

18 open-source-maven not reached The affected package being open source on Maven, so the fix can be read

19 poc-derivable not reached An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit not reached Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match not reached A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc not reached Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold not reached Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory

24 no-exploit-published not reached Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

NVD ↗ · CVE.org ↗