CVE-2021-22555: listed in the CISA KEV catalog

CVE-2021-22555 · CVSS 8.3 HIGH · EPSS 79% · KEV 2025-10-06

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

Is CVE-2021-22555 exploited?

• Listed in the CISA KEV catalog on 2025-10-06.
• Federal remediation due 2025-10-27.
• Past that date by 292 days.
• EPSS puts exploitation in the next 30 days at 79%.
• Public exploit code: packaged in a public tool.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

No patch identifier recorded here yet.

What PlainSec published about CVE-2021-22555

• Node Kernel Bugs on GKE COS Nodes Enable Host Escalation (2026-04-15)
• Google Cloud Issues Multiple Linux Kernel Privilege Escalation Fixes for GKE Nodes (2026-04-07)
• Multiple Linux Kernel Flaws Elevate Privileges on GCP Container Nodes (2026-04-03)
• Multiple High-Severity Cloud Vulnerabilities Impact Container Nodes (2026-04-01)

Primary sources

• NVD record
• CISA KEV catalog
• Metasploit: exploit/linux/local/netfilter_xtables_heap_oob_write_priv_esc
• Exploit-DB 50135

What this record does not say

• No affected package data.
• No patch identifier.

KEV and EPSS are re-checked daily. Record last updated 2026-08-15.