CVE-2026-53266 · Low · CISA KEV

Linux Kernel Out-of-Bounds Write: Critical for EoL Systems

Threat Engine Auto-Feed · data current as of 2026-09-18

A critical out-of-bounds write vulnerability in the Linux Kernel's ebtables SNAT target, CVE-2026-53266, allows for direct memory writes via ARP sender hardware address rewrite. This vulnerability is listed in CISA KEV, indicating active exploitation. Systems running end-of-life (EoL) or end-of-service (EoS) kernel versions are particularly at risk.

  • CVSS:
  • EPSS percentile: 0.02189
  • Exploitation pressure: 26/100 (Low)

Exploitation reality: listed in CISA KEV (exploited in the wild) · EPSS 2th percentile. Threat × Vulnerability from public signals — impact depends on your environment.

Weakness —

This vulnerability involves an out-of-bounds write, meaning a program attempts to write data beyond the allocated memory buffer. In this case, the ebtables SNAT target in the Linux Kernel can be tricked into writing an ARP sender hardware address directly into a sensitive memory area, potentially corrupting data or executing malicious code.

Who's at risk

Exposure: unknown · Auth: unknown · unknown

Enterprise profiles most at risk

  • Organizations utilizing Linux systems with end-of-life (EoL) or end-of-service (EoS) kernel versions
  • Financial services organizations
  • Technology sector organizations

Misconfigurations that escalate it

  • Continued operation of unsupported Linux Kernel versions
  • Lack of network segmentation allowing unauthenticated ARP traffic manipulation

High-impact scenarios

  • System compromise leading to data exfiltration or integrity loss
  • Denial of service due to memory corruption
  • Lateral movement within a compromised network
  • Ransomware deployment by financially motivated actors

Likely adversaries

  • FIN7 — Financial services (Assessed)
  • LockBit affiliates — Financial services (Assessed)
  • APT38 (Lazarus) — Financial services (Assessed)
  • APT29 (Cozy Bear) — Technology (Assessed)
  • Scattered Spider — Technology (Assessed)

What to do (defensive)

Detect

  • Monitor for unusual ARP traffic patterns, especially those involving sender hardware address rewrites
  • Scan for Linux systems running unsupported kernel versions
  • Implement network intrusion detection systems (NIDS) to flag suspicious ebtables activity

Contain

  • Isolate affected systems from critical networks
  • Block suspicious ARP traffic at network perimeters
  • Disable ebtables SNAT functionality if not critical and if feasible

Patch

  • Transition all Linux Kernel instances to supported versions immediately
  • Apply vendor-provided patches for CVE-2026-53266 as they become available for supported versions

Frontier verdict — Low

Prioritize patching or discontinuing use of EoL/EoS Linux Kernel versions due to active exploitation and potential for critical system compromise.

For detection-engineering and awareness only · point-in-time · not security advice · sourced from NVD, FIRST EPSS, CISA KEV. Adversary mappings are assessments unless cited.