Vulnerability in Xiangshan Nemu
CVE-2026-29649
NEMU contains an implementation flaw in its RISC-V Hypervisor CSR handling where henvcfg[7:4] (CBIE/CBCFE/CBZE-related fields) is incorrectly masked/updated based on menvcfg[7:4], so a machine-mode write to menvcfg can implicitly modify the hypervisor's environment configuration. This can lead to incorrect enforcement of virtualization configuration and may cause unexpected traps or denial of service when executing cache-block management instructions in virtualized contexts (V=1).
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (49.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 49.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/OpenXiangShan/NEMU/issues/681 (Issue Tracking)
- github.com/OpenXiangShan/NEMU/pull/689 (Patch, Issue Tracking)
- docs.riscv.org/reference/isa/priv/machine.html (Product)
- docs.riscv.org/reference/isa/priv/hypervisor.html (Product)
Frequently asked questions
- What is CVE-2026-29649?
- CVE-2026-29649 is a critical-severity vulnerability in Xiangshan Nemu, classified under Protection Mechanism Failure. CVSS score: 9.8/10. Published 2026-04-20.
- How severe is CVE-2026-29649?
- Critical severity. CVSS v3 base score is 9.8 out of 10.