Linux kernel NFULA_PAYLOAD padding leak in nfnetlink_log
CVE-2026-31428 Published on April 13, 2026
netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD
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.
Products Associated with CVE-2026-31428
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Affected Versions
Linux:- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below fc961dd7272b5e4a462999635e44a4770d7f2482 is affected.
- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below a8365d1064ded323797c5e28e91070c52f44b76c is affected.
- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below a2f6ff3444b663d6cfa63eadd61327a18592885a is affected.
- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below c9f6c51d36482805ac3ffadb9663fe775a13e926 is affected.
- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below 7eff72968161fb8ddb26113344de3b92fb7d7ef5 is affected.
- Version df6fb868d6118686805c2fa566e213a8f31c8e4f and below 52025ebaa29f4eb4ed8bf92ce83a68f24ab7fdf7 is affected.
- Version 2.6.24 is affected.
- Before 2.6.24 is unaffected.
- Version 6.1.168, <= 6.1.* is unaffected.
- Version 6.6.131, <= 6.6.* is unaffected.
- Version 6.12.80, <= 6.12.* is unaffected.
- Version 6.18.21, <= 6.18.* is unaffected.
- Version 6.19.11, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.