CVE-2026-31428

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD __build_packet_message() manually constructs the NFULA_PAYLOAD netlink attribute using skb_put() and skb_copy_bits(), bypassing the standard nla_reserve()/nla_put() helpers. While nla_total_size(data_len) bytes are allocated (including NLA alignment padding), only data_len bytes of actual packet data are copied. The trailing nla_padlen(data_len) bytes (1-3 when data_len is not 4-byte aligned) are never initialized, leaking stale heap contents to userspace via the NFLOG netlink socket. Replace the manual attribute construction with nla_reserve(), which handles the tailroom check, header setup, and padding zeroing via __nla_reserve(). The subsequent skb_copy_bits() fills in the payload data on top of the properly initialized attribute.

References

• https://git.kernel.org/stable/c/52025ebaa29f4eb4ed8bf92ce83a68f24ab7fdf7
• https://git.kernel.org/stable/c/7eff72968161fb8ddb26113344de3b92fb7d7ef5
• https://git.kernel.org/stable/c/a2f6ff3444b663d6cfa63eadd61327a18592885a
• https://git.kernel.org/stable/c/a8365d1064ded323797c5e28e91070c52f44b76c
• https://git.kernel.org/stable/c/c9f6c51d36482805ac3ffadb9663fe775a13e926