IRONSMITHINTEL
HIGHCVSS8.3
|
Actively Exploited
|CISA KEV|CVE-2021-22555|Auth: none — unauthenticated|Reboot: required|Manual only

Linux Kernel Heap Out-of-Bounds Write Vulnerability (CVE-2021-22555)

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.

Published Jul 7, 2021 · Updated May 17, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

An attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2025-10-27 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Out-of-bounds Write (CWE-787) vulnerability in Linux Kernel. 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 Exploitation requires adjacent_network access, higher attack complexity, no authentication required, and no user interaction required.

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security
●Running c400 firmware: -; c250 firmware: -; h410c firmware: -; h300s firmware: -; h500s firmware: -; h700s firmware: -; h410s firmware: -; linux kernel: 2.6.19 ≤ v < 4.4.267, 4.5 ≤ v < 4.9.267, 4.10 ≤ v < 4.14.231, 4.15 ≤ v < 4.19.188, 4.20 ≤ v < 5.4.113, 5.5 ≤ v < 5.10.31, 5.11 ≤ v < 5.12; fabric operating system: -; fas 8300 firmware: -; fas 8700 firmware: -; aff a400 firmware: -; aff a250 firmware: -; aff 500f firmware: -; h610c firmware: -; h610s firmware: -; h615c firmware: -; cloud backup: -; hci management node: -; solidfire: -
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html

How to patch

Manual remediation steps

1
Identify affected hosts: query inventory for general installs in scope.
2
Apply the vendor security update referenced in CVE-2021-22555's advisory. No specific KB/version is encoded yet — consult the linked MSRC/vendor URL.
3
Verify the fix per the vendor's published verification steps.
4
Document the remediation in your change ticket and re-scan with your vulnerability scanner to confirm closure.
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2021-22555↗ MSRC Advisory↗ NVD↗ Vendor Advisory