Exploited vulnerability · CISA KEV
Yes. CVE-2026-53266, Linux Kernel Out-of-Bounds Write Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 18 Sep 2026, 85 days after it was published. It affects Linux Kernel. If you run it, CISA's required action is: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
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 product(s) 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.
| Vendor | Linux (32 exploited CVEs in KEV) |
| Product | Kernel |
| Vulnerability | Linux Kernel Out-of-Bounds Write Vulnerability |
| Weakness | CWE-787 |
| Published | 25 Jun 2026 |
| Added to KEV | 18 Sep 2026 |
| Reported by (CNA) | Linux |
Yes. CISA added CVE-2026-53266 to the Known Exploited Vulnerabilities catalog on 18 Sep 2026, which means there is reliable evidence of exploitation in the wild.
CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. Check Linux's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Kernel and watch it for signs of compromise.
Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in September 2026 · Linux scorecard · act-now radar.
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