CVE-2026-31428 netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD
A local attacker can read uninitialized kernel heap memory via the NFLOG netlink socket due to missing padding initialization in packet logging.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-31428?
CVE-2026-31428 is a medium-severity vulnerability in Linux kernel, published on 13 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-908
Which versions are affected by CVE-2026-31428?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31428?
Apply the vendor's patch.
Is CVE-2026-31428 being exploited?
There is no known exploitation of CVE-2026-31428 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-82724, BELL-CVE-2026-31428, DEBIAN-CVE-2026-31428, GHSA-mp33-36gg-v9h7, ROOT-OS-DEBIAN-11-CVE-2026-31428, ROOT-OS-DEBIAN-12-CVE-2026-31428 and 4 more.