VDB-358367 · CVE-2026-29646 · ID 951

OpenXiangShan NEMU Hypervisor Extension access control

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
5.3	$0-$5k	0.00

Summaryinfo

A vulnerability identified as critical has been detected in OpenXiangShan NEMU. This impacts an unknown function of the component Hypervisor Extension. The manipulation leads to access control. This vulnerability is uniquely identified as CVE-2026-29646. No exploit exists. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability was found in OpenXiangShan NEMU (affected version not known) and classified as critical. This issue affects some unknown functionality of the component Hypervisor Extension. The manipulation with an unknown input leads to a access control vulnerability. Using CWE to declare the problem leads to CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at docs.riscv.org. The identification of this vulnerability is CVE-2026-29646 since 03/04/2026. The exploitation is known to be easy. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

Applying the patch 55295c4 is able to eliminate this problem. The bugfix is ready for download at github.com.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

OpenXiangShan

Name

NEMU

Website

Product: https://github.com/OpenXiangShan/NEMU/

CPE 2.3info

🔒

CPE 2.2info

🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.3

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Access control
CWE: CWE-284 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 55295c4

Timelineinfo

03/04/2026 CVE reserved
04/21/2026 +47 days Advisory disclosed
04/21/2026 +0 days VulDB entry created
04/21/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: 951
Status: Confirmed

CVE: CVE-2026-29646 (🔒)
GCVE (CVE): GCVE-0-2026-29646
GCVE (VulDB): GCVE-100-358367

Entryinfo

Created: 04/21/2026 06:45
Changes: 04/21/2026 06:45 (56)
Complete: 🔍
Cache ID: 216::103