CVE-2026-74751: Linux Vulnerability (CVSS 9.4)

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 bytes fit within the first word. With the adjusted boundary, t4 can equal t0, and entering the loop with stale register state from the first-word processing would produce incorrect results. The final minu clamp ensures the result is still correct when the last loaded word extends past s + count - 1 within the same aligned word.

Metrics

CVSS 3.1

9.4/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 5ba15d419fab848a3813eb56bbcad00e291fbc49, < e697e30f3dd2da3a1df7dc0980546d5b53aea4b6; >= 5ba15d419fab848a3813eb56bbcad00e291fbc49, < 5d588c684833e678a0008eb69c33190f01a65f4b
Linux	Linux	7.1

References

Timeline

Published: Aug 26, 2026
Last Modified: Aug 27, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-74751?

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 bytes fit within the first word. With the adjusted boundary, t4 can equal t0, and entering the loop with stale register state from the first-word processing would produce incorrect results. The final minu clamp ensures the result is still correct when the last loaded word extends past s + count - 1 within the same aligned word.

How severe is CVE-2026-74751?

CVE-2026-74751 has a CVSS score of 9.4/10 (CRITICAL severity).

How do I fix CVE-2026-74751?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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