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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 20:27 UTC

Brocade, Linux, Netapp · Fabric Operating System, Kernel, Linux Kernel +19 more

CVE-2021-22555

Linux Kernel Heap Out-of-Bounds Write Vulnerability

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

View response plan
CVSS7.8
EPSS78.7%
KEVYes
ExploitationConfirmed exploitation
RemediationExplicit patch identified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 78.7%; technical severity is CVSS 7.8.

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

Who should care

  • Teams operating Fabric Operating System, Kernel, Linux Kernel +19 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Fabric Operating System, Kernel, Linux Kernel +19 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. 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. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Patch

Required Action

Technical details

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-787
Affected versions
Brocade Fabric Operating System (Version -); Linux Kernel; Linux Linux Kernel (Start Including 2.6.19, End Excluding 4.4.267 | Start Including 4.5, End Excluding 4.9.267 | Start Including 4.10, End Excluding 4.14.231 | Start Including 4.15, End Excluding 4.19.188); Netapp Aff 500f Firmware (Version -); Netapp Aff A250 Firmware (Version -); Netapp Aff A400 Firmware (Version -); Netapp C250 Firmware (Version -); Netapp C400 Firmware (Version -)
Fixed versions
Linux Linux Kernel (Fixed from 4.4.267, 4.9.267, 4.14.231, 4.19.188, 5.4.113, 5.10.31, 5.12)
Published
7 July 2021
Attack vector
Local
Privileges required
Low
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 78.7%
  4. Signal calculated at 81

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.