CVE-2026-74544: net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds u32_change() copies the user-provided tc_u32_sel.offshift (unsigned char, 0-255) into the kernel knode object without bounds validation. When a packet later hits u32_classify() with TC_U32_VAROFFSET set, it evaluates `ntohs(offmask & *data) >> offshift` where the left operand is a 16-bit value promoted to a 32-bit int. Any offshift >= 32 is undefined behavior per C11 6.5.7p3, triggerable by an unprivileged user via user/network namespaces. UBSAN: shift-out-of-bounds in net/sched/cls_u32.c:236:43 shift exponent 32 is too large for 32-bit type int Fix this by rejecting offshift >= 16 during filter creation in u32_change().

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 724c8edbacf1259988829cb9967f751222121d8aaffected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 006a4598da9a6b02e0ddc3ca5042b97224774364affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 9990cac513e8b191de2ee589051ea7ebf3cee940affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 313cb9ffc4101a885d791facf4b5ea3d5e06144daffected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < aef96eead2860cbfa371e4471d4f04412213b958affected

Linux Linux

Default version status: affected

2.6.12affected
0 to < 2.6.12unaffected
6.6.160 to ≤ 6.6.*unaffected
6.12.114 to ≤ 6.12.*unaffected
6.18.57 to ≤ 6.18.*unaffected
7.1.8 to ≤ 7.1.*unaffected
7.2 to ≤ *unaffected

CVE-2026-74544

net/sched: cls_u32: validate offshift to prevent shift-out-of-bounds

Description

Affected products

Linux Linux

Linux Linux

References