Linux kernel: nft_payload offload mask bug due to 32-bit shift overflow
CVE-2026-74579 Published on August 17, 2026
netfilter: nft_payload: fix mask build for partial field offload
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_payload: fix mask build for partial field offload
nft_payload_offload_mask() builds the offload match mask for a payload
expression that covers only part of a header field. For a partial IPv6
address match (field_len = 16, priv_len = 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.
Products Associated with CVE-2026-74579
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Affected Versions
Linux:- Version a5d45bc0dc50f9dd83703510e9804d813a9cac32 and below b19b5d2e042c294e2cc1c908dc598f9d64015396 is affected.
- Version a5d45bc0dc50f9dd83703510e9804d813a9cac32 and below a375d8ace807767f29f276b681b6324c74929b1d is affected.
- Version a5d45bc0dc50f9dd83703510e9804d813a9cac32 and below 16b553c46e347bc9de9946c4960654d5884a86de is affected.
- Version a5d45bc0dc50f9dd83703510e9804d813a9cac32 and below 630295d5bba1d0e0f494cc459452eb0a0058c545 is affected.
- Version a5d45bc0dc50f9dd83703510e9804d813a9cac32 and below 39e88f28fb32bf02bd4b525c24c842c9cff5663d is affected.
- Version 5c2b4b4f9fa5b765b927e361e3d310bcb5773015 is affected.
- Version 5.9.14 and below 5.10 is affected.
- Version 5.10 is affected.
- Before 5.10 is unaffected.
- Version 6.6.151, <= 6.6.* is unaffected.
- Version 6.12.103, <= 6.12.* is unaffected.
- Version 6.18.44, <= 6.18.* is unaffected.
- Version 7.1.8, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.