CVE-2026-74751

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

riscv: lib: Fix ZBB strnlen reading past count boundary

The ZBB-optimized strnlen loop loads one word ahead before checking the

aligned boundary:

REG_L t1, SZREG(t0) // load next word

addi t0, t0, SZREG // advance

orc.b t1, t1

bgeu t0, t4, 4f // boundary check AFTER load

where t4 = (s + count) & -SZREG. When s is aligned and count is a

multiple of SZREG, t4 equals s + count and the loop loads a full word

starting at exactly s + count. If s + count falls on a page boundary

with the next page unmapped, this faults.

Fix by computing the aligned boundary from the last valid byte

(s + count - 1) instead of s + count. This makes the loop stop at the

word containing the last valid byte rather than potentially loading the

word after it. The count == 0 case is already handled by the beqz

early exit.

Also add a pre-loop guard (bgeu t0, t4) for the case where all valid

byte

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References