Linux Kernel EUVD-2026-38853

The affected component is the netdevsim driver in the Linux kernel (CPE: cpe:2.3:a:linux:linux), a network device simulator designed primarily for kernel development and testing rather than production workloads. The function nsim_dev_trap_skb_build constructs a dummy socket buffer (sk_buff) to simulate packet trapping; it previously called skb_put to reserve space for struct iphdr without zero-initializing it, meaning heap memory at that allocation may contain stale kernel data from prior use. CWE-908 (Use of Uninitialized Resource) describes this class of defect: reading or transmitting uninitialized memory regions can result in undefined behavior (leading to crashes or denial of service) or inadvertent disclosure of kernel memory contents to userspace or network observers. The KMSAN (Kernel Memory Sanitizer) dynamic analysis tool via syzbot detected the uninit-value read, which is the canonical mechanism for catching this class of kernel vulnerability.