High severity · published Jul 7, 2021
CVE-2021-22555
Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE
In wildKEV
7.8
CVSS
78.7%
EPSS
Yes
On KEV
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
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)78.7% · higher than 100% of CVEs
Exploited in the wildYes
CISA KEVListed Oct 6, 2025
Federal remediation dueOct 27, 2025
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
2.6.19-rc1 before unspecified · source: vendor, NVD, KEV
A5
Aff 500f Firmware · Netapp
All versions, or not specified · source: NVD
AA
Aff A250 Firmware · Netapp
All versions, or not specified · source: NVD
AA
Aff A400 Firmware · Netapp
All versions, or not specified · source: NVD
CF
C250 Firmware · Netapp
All versions, or not specified · source: NVD
CF
C400 Firmware · Netapp
All versions, or not specified · source: NVD
CB
Cloud Backup · Netapp
All versions, or not specified · source: NVD
FO
Fabric Operating System · Broadcom
All versions, or not specified · source: NVD
F8
Fas 8300 Firmware · Netapp
All versions, or not specified · source: NVD
F8
Fas 8700 Firmware · Netapp
All versions, or not specified · source: NVD
HF
H300s Firmware · Netapp
All versions, or not specified · source: NVD
HF
H410c Firmware · Netapp
All versions, or not specified · source: NVD
In the news
VulnerabilityHigh
[CISA KEV] CVE-2021-22555: Linux Kernel - 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.
KEKernelCVE-2021-22555
Oct 6, 2025·CISA KEV
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-22555
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-22555
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
x_refsource_MISC
https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528
x_refsource_MISC
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21
x_refsource_MISC
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d
x_refsource_MISC
http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html
x_refsource_CONFIRM
https://security.netapp.com/advisory/ntap-20210805-0010/
x_refsource_MISC
http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html
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