HIGH CVSS 7.5
Published: 2026-04-20

CVE-2026-29645

xiangshan nemu Security Advisory (CVE-2026-29645)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-29645 impacting xiangshan nemu. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
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.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product xiangshan / nemu
Affected Versions 2025.12
Weakness Enumeration CWE-131

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-29645 impacting xiangshan nemu.

⚡ Nuclei Detection Template (YAML) cve-2026-29645.yaml
id: cve-2026-29645

info:
  name: xiangshan nemu - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-29645 affecting xiangshan nemu.
    Evaluation: NEMU (OpenXiangShan/NEMU) before v2025.12.r2 contains an improper instruction-validation flaw in its RISC-V Vector (RVV) decoder. The decoder does not...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-29645
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 7.5
    cve-id: CVE-2026-29645
    cwe-id: CWE-131
  tags: cve,cve-2026-29645,xiangshan,nemu,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "nemu"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-29645.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-29645
# Target: xiangshan nemu | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-29645 (xiangshan nemu)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against xiangshan nemu scope (2025.12).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-29645.sh
# Recommended Remediation & Patching Commands for CVE-2026-29645
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install nemu 2>/dev/null || \
sudo dnf upgrade nemu 2>/dev/null || \
sudo yum update nemu

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i nemu 2>/dev/null || rpm -qa | grep -i nemu

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-29645 in xiangshan nemu?

Review vendor-specific security notices and update xiangshan nemu packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-29645?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-29645?

CVE-2026-29645 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2026-29645
Weakness CWE-131
Vendor xiangshan
Product nemu
Published 2026-04-20
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H