Linux Kernel Netfilter net/netfilter/x_tables.c out-of-bounds write

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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8.2$0-$5k0.00

Summaryinfo

A vulnerability has been found in Linux Kernel and classified as critical. This impacts an unknown function of the file net/netfilter/x_tables.c of the component Netfilter. The manipulation leads to out-of-bounds write. This vulnerability is referenced as CVE-2021-22555. Remote exploitation of the attack is possible. Furthermore, an exploit is available. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability was found in Linux Kernel (Operating System) (the affected version unknown). It has been rated as critical. This issue affects an unknown part of the file net/netfilter/x_tables.c of the component Netfilter. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability.

The weakness was published 07/08/2021. It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2021-22555. Technical details as well as a public exploit are known.

The exploit is available at packetstormsecurity.com. It is declared as attacked. We expect the 0-day to have been worth approximately $25k-$100k. The vulnerability scanner Nessus provides a plugin with the ID 208651 (CentOS 7 : kpatch-patch (RHSA-2021:3381)), which helps to determine the existence of the flaw in a target environment. The CISA Known Exploited Vulnerabilities Catalog lists this issue since 10/06/2025 with a due date of 10/27/2025:

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

Applying a patch is able to eliminate this problem. The bugfix is ready for download at git.kernel.org.

The vulnerability is also documented in the databases at Exploit-DB (50135), Tenable (208651) and EUVD (EUVD-2021-9696). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.3
VulDB Meta Temp Score: 8.2

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔍

CNA Base Score: 8.3
CNA Vector (Google Inc.): 🔍

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Out-of-bounds write
CWE: CWE-787 / CWE-119
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔍
Access: Public
Status: Attacked
Download: 🔍

EPSS Score: 🔍
EPSS Percentile: 🔍

KEV Added: 🔍
KEV Due: 🔍
KEV Remediation: 🔍
KEV Ransomware: 🔍
KEV Notice: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 208651
Nessus Name: CentOS 7 : kpatch-patch (RHSA-2021:3381)

Exploit-DB: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔍

Patch: git.kernel.org

Timelineinfo

01/05/2021 🔍
07/08/2021 +183 days 🔍
07/08/2021 +0 days 🔍
12/30/2025 +1636 days 🔍

Sourcesinfo

Vendor: kernel.org

Advisory: github.com
Status: Confirmed

CVE: CVE-2021-22555 (🔍)
GCVE (CVE): GCVE-0-2021-22555
GCVE (VulDB): GCVE-100-178055
EUVD: 🔍
scip Labs: https://www.scip.ch/en/?labs.20161013

Entryinfo

Created: 07/08/2021 08:45
Updated: 12/30/2025 22:35
Changes: 07/08/2021 08:45 (40), 07/10/2021 10:05 (5), 07/10/2021 10:10 (1), 08/08/2024 20:00 (23), 09/16/2024 19:53 (1), 10/10/2024 01:53 (2), 10/06/2025 20:34 (13), 10/07/2025 04:02 (28), 12/30/2025 22:35 (1)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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