CVE-2021-22555
HighExploitedPublic exploitA heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c.
Published Sep 1, 2021 · Updated Oct 14, 2026 · Also known as A-184847809, DEBIAN-CVE-2021-22555, LSN-0080-1, LSN-0081-1, PUB-A-184847809, SUSE-SU-2021:2408-1, SUSE-SU-2021:2409-1, SUSE-SU-2021:2415-1, SUSE-SU-2021:2438-1, SUSE-SU-2021:2487-1, SUSE-SU-2021:2559-1, SUSE-SU-2021:2599-1, SUSE-SU-2021:2599-2, UBUNTU-CVE-2021-22555, UBUNTU-CVE-2021-3653, UBUNTU-CVE-2021-3656, USN-5039-1
Key Facts
Patch immediately- CVE-2021-22555 is a high-severity vulnerability (CVSS 7.8 v3.1) affecting Cloud Backup (Netapp), Hci Management Node (Netapp), Solidfire (Netapp) and 22 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 18, 2024. Public exploit code is available.
- EPSS estimates a 79% probability of exploitation in the next 30 days.
- Fixed versions are available, including :linux_kernel: :2021-10-05, bpftool 3.10.0-1160.41.1.el7, bpftool 4.18.0-305.12.1.el8_4.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
79%
Higher than 99.5% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-22555 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Oct 6, 2025 | Oct 27, 2025 | Not reported |
| Industry KEV feed | Mar 18, 2024 | Oct 27, 2025 | Not reported |
| CIRCL KEV | Oct 6, 2025 | Oct 27, 2025 | Not reported |
| ENISA EUVD | Oct 6, 2025 | n/a | Not reported |
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.
Affected Products
971 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Cloud BackupNetapp | See advisory | n/a |
| Hci Management NodeNetapp | See advisory | n/a |
| SolidfireNetapp | See advisory | n/a |
| Solidfire Baseboard Management ControllerNetapp | See advisory | n/a |
| Fabric Operating SystemBroadcom | See advisory | n/a |
Patched Releases
:linux_kernel:
:2021-10-05
bpftool
3.10.0-1160.41.1.el7, 4.18.0-305.12.1.el8_4
cluster-md-kmp-64kb
5.3.18-59.16.1
cluster-md-kmp-azure
5.3.18-38.14.1
cluster-md-kmp-default
4.12.14-122.80.1, 4.12.14-150.75.1, 4.12.14-197.99.1, 4.12.14-95.80.1, 4.4.180-94.147.1, 5.3.18-24.75.3, 5.3.18-59.16.1
cluster-md-kmp-preempt
5.3.18-59.16.1
cluster-md-kmp-rt
4.12.14-10.54.1, 5.3.18-45.3
dlm-kmp-64kb
5.3.18-59.16.1
dlm-kmp-azure
5.3.18-38.14.1
dlm-kmp-default
4.12.14-122.80.1, 4.12.14-150.75.1, 4.12.14-197.99.1, 4.12.14-95.80.1, 4.4.180-94.147.1, 5.3.18-24.75.3, 5.3.18-59.16.1
dlm-kmp-preempt
5.3.18-59.16.1
dlm-kmp-rt
4.12.14-10.54.1, 5.3.18-45.3
gfs2-kmp-64kb
5.3.18-59.16.1
gfs2-kmp-azure
5.3.18-38.14.1
gfs2-kmp-default
4.12.14-122.80.1, 4.12.14-150.75.1, 4.12.14-197.99.1, 4.12.14-95.80.1, 4.4.180-94.147.1, 5.3.18-24.75.3, 5.3.18-59.16.1
gfs2-kmp-preempt
5.3.18-59.16.1
gfs2-kmp-rt
4.12.14-10.54.1, 5.3.18-45.3
kernel
0:2.6.32-754.58.1.el6, 0:3.10.0-514.92.1.el7, 0:4.18.0-147.52.1.el8_1, 3.10.0-1160.41.1.el7, 4.14.231-173.360.amzn2, 4.18.0-305.12.1.el8_4
kernel-64kb
5.3.18-59.16.1
kernel-64kb-devel
5.3.18-59.16.1
kernel-64kb-extra
5.3.18-59.16.1
kernel-64kb-livepatch-devel
5.3.18-59.16.1
kernel-64kb-optional
5.3.18-59.16.1
kernel-abi-stablelists
4.18.0-305.12.1.el8_4
kernel-abi-whitelists
3.10.0-1160.41.1.el7
Timeline
Publicly disclosed
Sep 1, 2021
Added to Industry KEV feed
Mar 18, 2024
Added to CISA KEV
Oct 6, 2025
Added to CIRCL KEV
Oct 6, 2025
Added to ENISA EUVD
Oct 6, 2025
Last updated
Oct 14, 2026
Weakness Type
- CWE-787 Out-of-bounds Write
References
- advisoryhttp://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html
- advisoryRHSA-2021:3044
- advisoryRHSA-2021:3057
- advisoryRHSA-2021:3088
- advisoryRHSA-2021:3173
FAQ
Common Questions.
A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c.
Affected: Cloud Backup (Netapp); Hci Management Node (Netapp); Solidfire (Netapp), among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 18, 2024.
Yes. It was added on Oct 6, 2025 with a federal remediation due date of Oct 27, 2025.
Public exploit code is available.
Fixed versions are available, including :linux_kernel: :2021-10-05, bpftool 3.10.0-1160.41.1.el7, bpftool 4.18.0-305.12.1.el8_4.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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