CVE-2021-22555
Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE
Linux Kernel Heap Out-of-Bounds Write Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
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.
CISA notes
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21 ; https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d ; https://security.netapp.com/advisory/ntap-20210805-0010/ ; https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528 ; https://nvd.nist.gov/vuln/detail/CVE-2021-22555
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
Severity
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation Context
as of October 17, 2026- CISA added CVE-2021-22555 to the KEV catalog 1,552 days after its CVE record was published. The median for entries added in 2025 is 26 days.
- It is one of 31 Linux Kernel entries in the CISA KEV catalog, and one of 7 added in 2025.
- Its current EPSS score (78.7%) is higher than that of 63% of CISA KEV entries.
Affected Products
| Vendor | Product | Affected versions |
|---|---|---|
| - | Linux Kernel | 2.6.19-rc1 to <unspecified |
References
9 Links- https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d
- http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html
- https://security.netapp.com/advisory/ntap-20210805-0010/
- http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html
- http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html
- http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html
- http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html
Record Details
More from Linux Kernel
Linux Kernel Privilege Escalation Vulnerability
Linux Kernel Race Condition Vulnerability
Linux Kernel Improper Privilege Management Vulnerability
Linux Kernel Privilege Escalation Vulnerability
Related
Tool categories
CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.