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.
Analysis and contextual insights are available on OpenCVE Cloud.
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
Sign in to view the affected projects.
No advisories yet.
Mon, 17 Aug 2026 08:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-682 |
Mon, 17 Aug 2026 05:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | netfilter: nft_payload: fix mask build for partial field offload | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-17T05:28:27.768Z
Reserved: 2026-08-15T05:44:03.917Z
Link: CVE-2026-74579
No data.
Status : Received
Published: 2026-08-17T06:19:56.417
Modified: 2026-08-17T06:19:56.417
Link: CVE-2026-74579
No data.
OpenCVE Enrichment
Updated: 2026-08-17T08:00:05Z