Linux Kernel Out-of-Bounds Write Vulnerability
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Linux, fix it now.
CISA required action: 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.
US federal civilian agencies must remediate by Sep 21, 2026.
Official fix available since
Apply the vendor's update to every affected system. Check the fixed-in versions below where known.
Basis: NVD patch reference
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: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.
| Product | Vendor | Affected versions | Fixed in | Source |
|---|---|---|---|---|
| Linux | Linux | >= 5.4.73, < 5.5; >= 5.8.17, < 5.9; >= 5.9.2, < 5.10.259; >= 5.11, < 5.15.210; >= 5.16, < 6.1.176; >= 6.2, < 6.6.143 | 5.5; 5.9; 5.10.259; 5.15.210; 6.1.176; 6.6.143 | KEV |
Sources: KEV = CISA Known Exploited Vulnerabilities catalog.
Developments from the last 30 days, newest first.
CVE-2026-53266 scored CVSS 8.8: Linux Kernel, Linux Kernel Out-of-Bounds Write Vulnerability
CISA lists this as exploited in the wild. Unpatched Kernel systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
Patch released for CVE-2026-53266: Linux Kernel, Linux Kernel Out-of-Bounds Write Vulnerability
An official fix is now available for Linux Kernel. This vulnerability is being exploited, so apply it promptly.
Basis: NVD patch reference
CVE-2026-53266 added to CISA KEV: Linux Kernel, Linux Kernel Out-of-Bounds Write Vulnerability
CISA lists this as exploited in the wild. Unpatched Kernel systems are exposed to active attacks now.
Basis: CISA Known Exploited Vulnerabilities catalog
CISA lists this as exploited in the wild. Unpatched Linux systems are exposed to active attacks now.
Apply the vendor's security update for Linux.
