CVE-2021-22555
Linux Kernel Heap Out-of-Bounds Write Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 27 October 2025). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 78.68% probability · 100th percentile
- CISA KEV
- Listed 6 October 2025 · due 27 October 2025
- Weakness
- CWE-787
- Affected
- netapp/c400 firmware · netapp/c250 firmware · netapp/h410c firmware · netapp/h300s firmware · netapp/h500s firmware · netapp/h700s firmware · netapp/h410s firmware · linux/linux kernel · brocade/fabric operating system · netapp/fas 8300 firmware · netapp/fas 8700 firmware · netapp/aff a400 firmware · netapp/aff a250 firmware · netapp/aff 500f firmware · netapp/h610c firmware · netapp/h610s firmware · netapp/h615c firmware · netapp/cloud backup · netapp/hci management node · netapp/solidfire · +1 more
- Source
- cve-coordination@google.com
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. 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
References
- http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.htmlThird Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlExploit, Third Party Advisory, VDB Entry
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21Mailing List, Patch, Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801dMailing List, Patch, Vendor Advisory
- https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528Exploit, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210805-0010/Third Party Advisory
- http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.htmlThird Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.htmlExploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.htmlExploit, Third Party Advisory, VDB Entry
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21Mailing List, Patch, Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801dMailing List, Patch, Vendor Advisory
- https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528Exploit, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210805-0010/Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22555US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.