CVE-2026-53266: Linux Kernel exploitation alert

CVE-2026-53266: what changed

CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on 2026-09-18. Inclusion indicates evidence of exploitation; it does not establish that your own systems have been compromised.

Affected product

Linux Kernel. Confirm affected versions against the vendor advisory.

CISA description

Linux Kernel contains an out-of-bounds write vulnerability in the ebtables SNAT target which allows an ARP sender hardware address rewrite to write directly into a nonlinear socket-buffer fragment backed by a splice-imported file page. The impacted products could be end-of-life EoL and/or end-of-service EoS. Users are advised to discontinue use and/or transition to a supported version.

Recommended response

Inventory affected deployments, check vendor guidance for fixes or mitigations, and verify the update was applied. Review available logs and incident-response guidance when exploitation is suspected.

Catalog context

CISA lists a remediation due date of 2026-09-21. Federal directive deadlines have a defined scope; other organizations should prioritize according to their exposure and risk. Ransomware campaign use is listed as unknown; “unknown” does not mean exploitation is absent.

Sources

• CISA Known Exploited Vulnerabilities catalog
• CVE-2026-53266 reference

Automated security brief based on CISA catalog data. Catalog addition date: 2026-09-18.