CVE-2026-74579 _ Linux kernel
In the Linux kernel, the following vulnerability has been resolved:
- netfilter: nft_payload: fix mask build for partial field offload
- nftpayloadoffload_mask() builds the offload match mask for a payload
expression that covers only part of a header field. For a partial IPv6 address match (fieldlen = 16, privlen = 1) that shift is 1 << 120, which is undefined on the 32-bit int operand. It also trims only one word, so the remaining words stay 0xffffffff (and when priv_len is a multiple of 4 the trim is skipped entirely), leaving the mask covering more bytes than the rule matches.
UBSAN: shift-out-of-bounds in net/netfilter/nft_payload.c:278:20 shift exponent 120 is too large for 32-bit type 'int'
...
The match is byte-granular and struct nft_data is zero-initialised, so the correct mask is simply the first priv_len bytes set to 0xff. Set those bytes directly and drop the word/shift trimming; this removes the undefined shift and no longer over-masks the trailing bytes.
References:
https://git.kernel.org/stable/c/16b553c46e347bc9de9946c4960654d5884a86de
https://git.kernel.org/stable/c/39e88f28fb32bf02bd4b525c24c842c9cff5663d
https://git.kernel.org/stable/c/630295d5bba1d0e0f494cc459452eb0a0058c545
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