CVE-2026-31428
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel's netfilter nfnetlink_log, an uninitialized heap memory leak was found in the NFULA_PAYLOAD attribute. The __build_packet_message() function manually constructs the attribute, copying only payload data without zeroing the padding bytes, leaking kernel heap contents to userspace.
Risk Assessment
A local attacker can read kernel heap memory via the NFLOG netlink socket, potentially obtaining sensitive data (e.g., keys, passwords) from other processes or the kernel itself.
Recommendation
Apply the Linux kernel patch for CVE-2026-31428, which replaces manual attribute construction with nla_reserve() that automatically zeroes padding.
Original NVD description (English source)
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.