CVE-2026-53266
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk3th percentile — higher than 3% of all known CVEs
Summary
A vulnerability was found in the Linux kernel's netfilter bridge module related to the ebtables SNAT rule. When rewriting the sender hardware address in ARP packets, skb_store_bits() may write to a non-writable skb fragment, potentially leading to data integrity issues. The fix ensures the MAC address range is made writable before modification.
Risk Assessment
An attacker could exploit this vulnerability to write data into protected kernel memory areas, potentially leading to privilege escalation or information disclosure. The risk is particularly relevant in environments using network bridging with ebtables rules.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 63137bc5882a or later). If an update is not possible, temporarily disable ebtables SNAT rules that modify the sender MAC address in ARP packets.
Original NVD description (English source)
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().