CVE-2026-29645: Xiangshan Nemu

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

NEMU (OpenXiangShan/NEMU) before v2025.12.r2 contains an improper instruction-validation flaw in its RISC-V Vector (RVV) decoder. The decoder does not correctly validate the funct3 field when decoding vsetvli/vsetivli/vsetvl, allowing certain invalid OP-V instruction encodings to be misinterpreted and executed as vset* configuration instructions rather than raising an illegal-instruction exception. This can be exploited by providing crafted RISC-V binaries to cause incorrect trap behavior, architectural state corruption/divergence, and potential denial of service in systems that rely on NEMU for correct execution or sandboxing.

Affected products

• Xiangshan Nemu: version 2025.12 only

Published 2026-04-20. Last modified 2026-06-17.