CVEs / CVE-2021-22555
CVE-2021-22555: Linux Kernel Heap Out-of-Bounds Write Vulnerability
- Known exploited in the CISA KEV catalog since 6 Oct 2025
- high 7.8 CVSS 3.1 (NVD)
- EPSS 78.6% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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 and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| n/a Linux Kernel | from 2.6.19-rc1, before unspecified | unspecified |
Exploitation
| In CISA KEV since | 6 Oct 2025 |
|---|---|
| Due date for US federal agencies | 27 Oct 2025 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 7.8 highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|---|
| Weakness | CWE-787 |
References
- CVE-2021-22555 on NVD
- CVE-2021-22555 in the CISA KEV catalog
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21 (cited by CISA)
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d (cited by CISA)
- https://security.netapp.com/advisory/ntap-20210805-0010/ (cited by CISA)
- https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528 (cited by CISA)
- CVE-2021-22555 on OSV
- http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-Bounds-Write.html Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html Exploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html Exploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html Exploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html Exploit, Third Party Advisory, VDB Entry
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=9fa492cdc160cd27ce1046cb36f47d3b2b1efa21 Mailing List, Patch, Vendor Advisory
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/netfilter/x_tables.c?id=b29c457a6511435960115c0f548c4360d5f4801d Mailing List, Patch, Vendor Advisory
- https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528 Exploit, 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-2021-22555 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.