Vulnerability in Xiangshan Nemu
CVE-2026-29645
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (52.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 52.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002
Affected products
- Xiangshan Nemu — versions 2025.12
Weakness classification (CWE)
References
- github.com/OpenXiangShan/NEMU/issues/952 (Issue Tracking)
- github.com/OpenXiangShan/NEMU/pull/958 (Issue Tracking)
- github.com/OpenXiangShan/NEMU/commit/481de637d5fc5838356caee80a79e56a33754039 (Patch)
- docs.riscv.org/reference/isa/unpriv/v-st-ext.html (Product)
Frequently asked questions
- What is CVE-2026-29645?
- CVE-2026-29645 is a high-severity vulnerability in Xiangshan Nemu, classified under Incorrect Calculation of Buffer Size. CVSS score: 7.5/10. Published 2026-04-20.
- How severe is CVE-2026-29645?
- High severity. CVSS v3 base score is 7.5 out of 10.