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[ CVE-2021-22555 · Published 7 Jul 2021 ]

Linux Kernel Heap Out-of-Bounds Write Vulnerability

Exploited · CISA KEV CVSS 7.8 EPSS 79%Fix available

[ Why it matters ]Priority signals

  • Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2025-10-06
  • EPSS: 79% chance of exploitation in the next 30 days (higher than 100% of CVEs)

[ Description ]Official 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

CISA: 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.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 27 Oct 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.

[ References ]References