CVE-2021-22555
HIGHCISA KEVEPSS 100th pctlDescription
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
How to fix
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This Red Hat / RHEL release reached end-of-life on 2020-11-30.
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Exploit Intelligence
Very high risk: more likely to be exploited than 100% of all known CVEs.
Linux Kernel Heap Out-of-Bounds Write Vulnerability
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.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Remediation due: 2025-10-27
References
Related Vulnerabilities
Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-22457 | Critical | 9.0 | 100% | KEV + Ransom | Fix |
| CVE-2025-0282 | Critical | 9.0 | 100% | KEV + Ransom | - |
| CVE-2023-4863 | High | 8.8 | 100% | KEV | Fix |
| CVE-2015-3113 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2021-20038 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2019-11043 | High | 8.7 | 100% | KEV + Ransom | Fix |
Common questions
How do I fix CVE-2021-22555?
Published advisories record a fix for 90 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2021-22555 being actively exploited?
Yes. CVE-2021-22555 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2025-10-27. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2021-22555?
CVE-2021-22555 has a CVSS v3 base score of 8.3, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-22555 affect?
Published advisories record a fix for kernel (Amazon), kernel-debuginfo (Amazon), kernel-debuginfo-common-aarch64 (Amazon), kernel-debuginfo-common-x86_64 (Amazon), and 86 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2021-22555
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.