cve 2026 23359

CVE-2026-23359 is a Linux kernel vulnerability in the BPF devmap code affecting XDP redirect operations. The flaw resides in the get_upper_ifindexes() function, which writes interface indices into an array without properly checking the array's capacity. This can lead to a stack-out-of-bounds write when a network device has more upper devices than expected, such as in configurations with many macvlan interfaces. The fix adds an explicit maximum parameter, stops writing once the buffer is full, and returns -EOVERFLOW to abort the redirect. This vulnerability is relevant for Linux system administrators and security professionals managing kernel updates and XDP-based networking.