VulnerabilityAnalyzed

CVE-2026-29645

NEMU (OpenXiangShan/NEMU) before v2025.12.r2 contains an improper instruction-validation flaw in its RISC-V Vector (RVV) decoder.

HIGH 7.5EPSS 0.54%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.54%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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.

CVSS 3.1: 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.54% probability · 44th percentile
CISA KEV: Not listed
Weakness: CWE-131, CWE-1287
Affected: xiangshan/nemu
Source: cve@mitre.org

References

https://docs.riscv.org/reference/isa/unpriv/v-st-ext.htmlProduct
https://github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039Patch
https://github.com/OpenXiangShan/NEMU/issues/952Issue Tracking
https://github.com/OpenXiangShan/NEMU/pull/958Issue Tracking

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.