CVE-2026-29646: OpenXiangShan NEMU · Privilege Defined With Unsafe Actions
Source CVE Database V5
Not known to be exploited · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
Users of OpenXiangShan NEMU should monitor vendor communications for updates and apply patches once available. Until then, consider limiting exposure of vulnerable NEMU instances or disabling RVH if feasible.
Description
A critical vulnerability exists in OpenXiangShan NEMU prior to commit 55295c4 when running with the RVH (Hypervisor extension) enabled. A VS-mode guest's write to the supervisor interrupt-enable CSR (sie) can be mishandled, affecting the machine-level interrupt enable state (mie). This flaw breaks privilege and virtualization isolation, potentially allowing denial of service or privilege-boundary violations in environments relying on NEMU for correct interrupt virtualization.
References
- docs.riscv.org/reference/isa/priv/machine.html (opens in a new tab)
- github.com/OpenXiangShan/NEMU/issues/951 (opens in a new tab)
- github.com/OpenXiangShan/NEMU/pull/938 (opens in a new tab)
- github.com/OpenXiangShan/NEMU/pull/938/commits/55295c46580456d8d5a9d5736e1fda924b8825ab (opens in a new tab)
- docs.riscv.org/reference/isa/unpriv/zicsr.html (opens in a new tab)
- docs.riscv.org/reference/isa/priv/supervisor.html (opens in a new tab)
- docs.riscv.org/reference/isa/priv/hypervisor.html (opens in a new tab)