DEBIAN-CVE-2026-53266

In the Linux kernel, the following vulnerability has been resolved:  netfilter: bridge: make ebtsnat ARP rewrite writable  The ebtables SNAT target keeps the Ethernet source address rewrite behind skbensurewritable(skb, 0).  This is intentional: at the bridge ebtables hooks the Ethernet header is addressed through skbmacheader()/ethhdr(), while skb->data points at the Ethernet payload.  Asking skbensurewritable() for ETHHLEN 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 skbstorebits() at an offset relative to skb->data:          skbstorebits(skb, sizeof(struct arphdr), info->mac, ETHALEN)  skbheaderpointer() 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, skbstorebits() 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 skbstorebits().