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CVE-2021-22555· NVD / CVE Program· CNA Google

Heap 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

HighCVSS 7.8 · v3.1KEVWeaponized Fix available
Published
Jul 7, 2021
Updated
Jun 16, 2026
EPSS
78.7% · 100th percentile
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Action score

85

Now

Patch today or shut off access.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
30 / 30 · Listed
EPSS
24 / 30 · 78.7%

CISA SSVC decision

Exploitation
active
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
7.8
CNA · Google
8.3
0.5 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Oct 6, 2025. That signals real attacks, not theory.

Remediation deadline for government agencies: Oct 27, 2025.

Affected systems

VendorProduct
linuxlinux kernel
netappc400 firmware
netappc400
netappc250 firmware
netappc250
netapph410c firmware
netapph410c
netapph300s firmware
netapph300s
netapph500s firmware
netapph500s
netapph700s firmware

and 24 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • brocade fabric operating systemall versions
  • linux linux kernel4.20 and later · before 5.4.113
  • linux linux kernel4.5 and later · before 4.9.267
  • linux linux kernel4.10 and later · before 4.14.231
  • linux linux kernel4.15 and later · before 4.19.188
  • linux linux kernel5.5 and later · before 5.10.31
  • linux linux kernel5.11 and later · before 5.12
  • linux linux kernel2.6.19 and later · before 4.4.267
  • netapp aff 500f firmwareall versions
  • netapp aff a250 firmwareall versions
  • netapp aff a400 firmwareall versions
  • netapp c250 firmwareall versions
  • netapp c400 firmwareall versions
  • netapp cloud backupall versions
  • netapp fas 8300 firmwareall versions
  • netapp fas 8700 firmwareall versions
  • netapp h300s firmwareall versions
  • netapp h410c firmwareall versions
  • netapp h410s firmwareall versions
  • netapp h500s firmwareall versions

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Google). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a Linux Kernel

    • 2.6.19-rc1 and later · before unspecifiedaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8kernel-tools-libs-develbefore 4.18.0-305.12.1.el8_44.18.0-305.12.1.el8_4
Debian:12linuxbefore 5.10.38-15.10.38-1
openSUSE:Leap 15.2kernel-debugbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-defaultbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-default-basebefore 5.3.18-lp152.84.1.lp152.8.38.15.3.18-lp152.84.1.lp152.8.38.1
openSUSE:Leap 15.2kernel-docsbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-kvmsmallbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-obs-buildbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-obs-qabefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-preemptbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-sourcebefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.2kernel-symsbefore 5.3.18-lp152.84.15.3.18-lp152.84.1
openSUSE:Leap 15.3kernel-64kbbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-azurebefore 5.3.18-38.14.15.3.18-38.14.1
openSUSE:Leap 15.3kernel-debugbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-debugbefore 4.12.14-197.99.14.12.14-197.99.1
openSUSE:Leap 15.3kernel-defaultbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-defaultbefore 4.12.14-197.99.14.12.14-197.99.1
openSUSE:Leap 15.3kernel-default-basebefore 5.3.18-59.16.1.18.8.15.3.18-59.16.1.18.8.1
openSUSE:Leap 15.3kernel-docsbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-kvmsmallbefore 4.12.14-197.99.14.12.14-197.99.1
openSUSE:Leap 15.3kernel-kvmsmallbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-obs-buildbefore 5.3.18-59.16.15.3.18-59.16.1
openSUSE:Leap 15.3kernel-obs-qabefore 5.3.18-59.16.15.3.18-59.16.1

+96

Other highest-scoring records for the same primary product.

  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
    83Now
  • CVE-2019-13272In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to creKEV
    77This week
  • CVE-2013-6282The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the v6k and v7 ARM platforms do not validate certain addKEV
    77This week
  • CVE-2013-2094The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9 uses an incorrect integer data type, which allows loKEV
    77This week
  • CVE-2014-3153The futex_requeue function in kernel/futex.c in the Linux kernel through 3.14.5 does not ensure that calls have two different futex addresseKEV
    72This week

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:kernel-tools-libs-devel4.18.0-305.12.1.el8_4 · AlmaLinux:8Package registry (OSV)
debian:linux5.10.38-1 · Debian:12Package registry (OSV)
opensuse:kernel-azure5.3.18-38.14.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:kernel-debug5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-default5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-default-base5.3.18-lp152.84.1.lp152.8.38.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-docs5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-kvmsmall5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-obs-build5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-obs-qa5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-preempt5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-source5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-source-azure5.3.18-38.14.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:kernel-syms5.3.18-lp152.84.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:kpatch-patch-4_18_0-3050:1-4.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_10_20:1-1.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_10_2-debuginfo0:1-1.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_10_2-debugsource0:1-1.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_3_10:1-3.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_3_1-debuginfo0:1-3.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_3_1-debugsource0:1-3.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_7_10:1-2.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_7_1-debuginfo0:1-2.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305_7_1-debugsource0:1-2.el8_4 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305-debuginfo0:1-4.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kpatch-patch-4_18_0-305-debugsource0:1-4.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
rocky linux:kernel0:4.18.0-305.12.1.el8_4 · Rocky Linux:8Package registry (OSV)
rocky linux:kernel-rt0:4.18.0-305.12.1.rt7.84.el8_4 · Rocky Linux:8Package registry (OSV)
suse:kernel-64kb5.3.18-59.16.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP3Package registry (OSV)
suse:kernel-azure4.12.14-16.65.1 · SUSE:Linux Enterprise Server 12 SP5Package registry (OSV)

+10

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

  • Metasploit module ×1
  • Exploit-DB entry ×1
  • Proof-of-concept repository on GitHub ×13

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
SourceKindDate
Exploit-DB entrylocal2021-07-15
Metasploit moduleexploit/linux/local/netfilter_xtables_heap_oob_write_priv_escNetfilter x_tables Heap OOB Write Privilege Escalationexploit2021-07-07
Proof-of-concept repository on GitHubstars:12021-07-15
Proof-of-concept repository on GitHubstars:142021-07-16
Proof-of-concept repository on GitHubstars:42021-07-16
Proof-of-concept repository on GitHubstars:12021-10-01
Proof-of-concept repository on GitHubstars:402022-04-05
Proof-of-concept repository on GitHubstars:12023-05-10
Proof-of-concept repository on GitHubstars:32023-08-05
Proof-of-concept repository on GitHubstars:02023-08-20
Proof-of-concept repository on GitHubstars:02024-02-05
Proof-of-concept repository on GitHubstars:02024-02-27

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Metasploitsame day
  2. Published
  3. First PoC+8 d
  4. CISA KEV+1552 d
  5. TodaySep 30, 2026+1912 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

We use this product, ask for help

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

All records