CVE-2021-22555

Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE

HIGH
7.8
CVSS Score
Published: July 7, 2021 at 11:20 AM UTC
Updated: October 13, 2026 at 06:25 PM UTC
21 products affected across 3 vendorsLinux KernelCloud BackupH700S Firmware· also runs on 15 platforms

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Severity
HIGH7.8
Exploitation
CISA KEV
Exploit prediction
EPSS 79%
SSVC
Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score78.7%

EPSS (Exploit Prediction Scoring System) estimates a 78.7% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

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.

Required Action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Ransomware Use
Unknown
Added to KEV
Oct 6, 2025
Remediation Due
Oct 27, 2025
370 days overdue

Description

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

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.6.19 ≤ v < 4.4.2674.10 ≤ v < 4.14.2314.15 ≤ v < 4.19.1884.20 ≤ v < 5.4.1134.5 ≤ v < 4.9.2675.11 ≤ v < 5.125.5 ≤ v < 5.10.312.6.19-rc1
Affected range stops below 4.14.231, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.19.188, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.4.267, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.9.267, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.10.31, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.4.113, so it looks safe — our inference, not a vendor statement
All versions
netapp-aff-500f (same device)
All versions
netapp-aff-a250 (same device)
All versions
netapp-aff-a400 (same device)
All versions
netapp-c250 (same device)
All versions
netapp-c400 (same device)
All versions
All versions
netapp-fas-8300 (same device)
All versions
netapp-fas-8700 (same device)

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

SSVC — Action Prioritization

SSVCActiveNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
LOCAL
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-787

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