CVE-2021-22555

HIGH8.3

CISA KEV

Published 2021-07-07 · Updated 2026-10-13 · Source cve-coordination@google.com

Summary

CVE-2021-22555 is a high-severity (CVSS 8.3) vulnerability in Linux Kernel. CISA added it to the Known Exploited Vulnerabilities catalog on October 6, 2025, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by October 27, 2025. CISA does not currently list it as used in ransomware campaigns. Linux has 32 vulnerabilities in the KEV catalog, 2 of them linked to ransomware.

All 32 known-exploited Linux vulnerabilities →

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

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

CWE-787CWE-787

CISA Known-Exploited Vulnerability

Product: Linux — Kernel

Name: Linux Kernel Heap Out-of-Bounds Write Vulnerability

Date added: 2025-10-06 · Due: 2025-10-27

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

References

View on NVD

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added 2026-09-18
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Kernel — Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability
added 2026-09-18
CVE-2026-53362
Kernel — Linux Kernel Unspecified Vulnerability
added 2026-08-27
CVE-2022-0995
Kernel — Linux Kernel Out-of-Bounds Write Vulnerability
added 2026-08-26

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