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Vulnerabilities

Vulnerability · CVE-2021-22555

Linux Kernel Heap Out-of-Bounds Write Vulnerability

Published Jul 7, 2021 · catalog updated Oct 13, 2026 · Linux Kernel

Patch now

CVE-2021-22555 is in the CISA known-exploited catalog, due Oct 27, 2025. Confirm Linux Kernel against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
High7.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
78.68%
Remediation
Remediation guidance
Affected products
cpe broadcom/fabric operating system · cpe linux/linux kernel · cpe netapp/aff a400 firmware · cpe netapp/c250 firmware · cpe netapp/c400 firmware · cpe netapp/fas 8300 firmware

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe broadcom/fabric operating systemversion unspecified
  • cpe linux/linux kernelversion unspecified
  • cpe netapp/aff a400 firmwareversion unspecified
  • cpe netapp/c250 firmwareversion unspecified
  • cpe netapp/c400 firmwareversion unspecified
  • cpe netapp/fas 8300 firmwareversion unspecified
  • cpe netapp/fas 8700 firmwareversion unspecified
  • cpe netapp/h300s firmwareversion unspecified
  • cpe netapp/h410c firmwareversion unspecified
  • cpe netapp/h410s firmwareversion unspecified
  • cpe netapp/h500s firmwareversion unspecified
  • cpe netapp/h700s firmwareversion unspecified
  • vendor Linux Kernelversion unspecified

How to fix CVE-2021-22555

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-22555 is in the CISA known-exploited catalog, due Oct 27, 2025. Confirm Linux Kernel against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What should an analyst verify?

CWE-787: Out-of-bounds Write. EPSS 78.68%. The CISA KEV listing is the exploitation evidence. A public exploit reference is linked in Sources. That is not the same as confirmed exploitation. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jul 7, 2021 · Catalog

    Detected

    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

  2. Oct 6, 2025 · CISA KEV

    Known exploited

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

  3. Oct 27, 2025 · CISA KEV

    Remediation due

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

  4. Oct 13, 2026 · Catalog

    Updated

    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

Sources

  • CISA KEVConfirmed exploitationCVE-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.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2021-22555

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-22555

    30-day exploitation probability 78.7%

    first.org
  • Exploit DatabasePublic exploit reference50135

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • Metasploit ModulesPublic exploit moduleexploit_linux/local/netfilter_xtables_heap_oob_write_priv_esc

    Public module reference (great). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-2021-22555

    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

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • VulnCheck KEVConfirmed exploitationCVE-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.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.