CVE intelligenceCISA KEV

CVE-2026-53266

Linux Kernel Out-of-Bounds Write Vulnerability

Published Jun 25, 2026Sources checked Nov 12, 2026

8.8HIGHCVSS out of 10

What this means

Actively exploited

CISA lists CVE-2026-53266 in its Known Exploited Vulnerabilities catalog, which means exploitation has been observed. The entry applies to Linux Kernel.

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.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Oct 9, 2026

Vendor remediation details

This update corrects flaws in the following subsystems: - ARM32 architecture; - ARM64 architecture; - MIPS architecture; - x86 architecture; - Intel NPU Driver; - Auxiliary display drivers; - Compressed RAM block device driver; - GPIO subsystem; - GPU drivers; - HID subsystem; - I2C subsystem; - IIO subsystem; - InfiniBand drivers; - Input Device core drivers; - Input Device (Mouse) drivers; - Multiple devices driver; - Media drivers; - Fastrpc Driver; - Ethernet bonding driver; - Network drivers; - Mellanox network drivers; - Microsoft Azure Network Adapter (MANA) driver; - Texas Instruments network drivers; - NVMEM (Non Volatile Memory) drivers; - Parport drivers; - SCSI subsystem; - SLIMbus drivers; - NVIDIA Tegra SoC drivers; - SPI subsystem; - Trusted Execution Environment drivers; -

Ubuntu Security Notices guidance

Vendor revision: Oct 9, 2026

Vendor remediation details

Ubuntu Security Notices guidance

Vendor revision: Oct 8, 2026

Vendor remediation details

CISA KEVListedObserved exploitation

EPSS0.9%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors1Source-linked actor relationships

Overview

What is CVE-2026-53266?

In the Linux kernel, the following vulnerability has been resolved:

netfilter: bridge: make ebt_snat ARP rewrite writable

The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is intentional: at the bridge ebtables hooks the Ethernet header is addressed through skb_mac_header()/eth_hdr(), while skb->data points at the Ethernet payload.

Asking skb_ensure_writable() for ETH_HLEN bytes would check the payload, not the Ethernet header, and would reintroduce the small packet regression fixed by commit 63137bc5882a.

However, the optional ARP sender hardware address rewrite is different. It writes through skb_store_bits() at an offset relative to skb->data:

skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN)

skb_header_pointer() only safely reads the ARP header; it does not make the later sender hardware address range writable. If that range is still held in a nonlinear skb fragment backed by a splice-imported file page, skb_store_bits() maps the frag page and copies the new MAC address directly into it.

Ensure the ARP SHA range is writable before reading the ARP header and before calling skb_store_bits().

Source: NVD

CISA says: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.CISA catalog due date Sep 21, 2026