CVE-2021-22555 — Linux Kernel Heap Out-of-Bounds Write Vulnerability

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

01What is this vulnerability?

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

02Affected products

Vendor	Product	Versions
n	a / Linux Kernel	2.6.19-rc1

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2025-10-06. Ransomware use: Unknown.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

Open in Sigma generator →

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2021-07-07T11:20:10.668Z
• Last modified: 2025-12-30T20:32:33.647Z
• Added to CISA KEV: 2025-10-06
• BOD 22-01 due: 2025-10-27

09References

• github.com — https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3…
• git.kernel.org — https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/ne…
• git.kernel.org — https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/ne…
• packetstormsecurity.com — http://packetstormsecurity.com/files/163528/Linux-Kernel-Netfilter-Heap-Out-Of-B…
• security.netapp.com — https://security.netapp.com/advisory/ntap-20210805-0010/
• packetstormsecurity.com — http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LS…
• packetstormsecurity.com — http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LS…
• packetstormsecurity.com — http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bound…
• packetstormsecurity.com — http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LS…