CVE-2026-53218

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nftexthdr: fix register tracking for FPRESENT flag

nftexthdrinit() passes user-controlled priv->len to nftparseregisterstore(), which marks that many bytes in the register bitmap as initialized. However, when NFTEXTHDRFPRESENT is set, the eval paths write only 1 byte (nftregstore8) or 4 bytes (*dest = 0 on TCP/DCCP error path). When len > 4, registers beyond the first are never written, retaining uninitialized stack data from nft_regs.

Bail out if userspace requests too much data when F_PRESENT is set.