CRITICAL CVSS 9.6
Published: 2026-03-31

CVE-2026-34449

b3log siyuan Security Advisory (CVE-2026-34449)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-34449 impacting b3log siyuan. Evaluated with CVSS Base Score of 9.6 (CRITICAL).

Original NVD Description

Source: NIST NVD
SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop running SiYuan by exploiting the permissive CORS policy (Access-Control-Allow-Origin: * + Access-Control-Allow-Private-Network: true) to inject a JavaScript snippet via the API. The injected snippet executes in Electron's Node.js context with full OS access the next time the user opens SiYuan's UI. No user interaction is required beyond visiting the malicious website while SiYuan is running. This issue has been patched in version 3.6.2.

📊 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
Required (UI:R)
User must click or open resource
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product b3log / siyuan
Affected Versions *
Weakness Enumeration CWE-942

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-2026-34449 impacting b3log siyuan.

⚡ Nuclei Detection Template (YAML) cve-2026-34449.yaml
id: cve-2026-34449

info:
  name: b3log siyuan - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: critical
  description: |
    Automated signature & scanner for CVE-2026-34449 affecting b3log siyuan.
    Evaluation: SiYuan is a personal knowledge management system. Prior to version 3.6.2, a malicious website can achieve Remote Code Execution (RCE) on any desktop r...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-34449
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
    cvss-score: 9.6
    cve-id: CVE-2026-34449
    cwe-id: CWE-942
  tags: cve,cve-2026-34449,b3log,siyuan,critical

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "siyuan"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-34449.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-34449
# Target: b3log siyuan | CVSS: 9.6 (CRITICAL)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-34449 (b3log siyuan)...")
    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 b3log siyuan scope (*).")
        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-2026-34449.sh
# Recommended Remediation & Patching Commands for CVE-2026-34449
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install siyuan 2>/dev/null || \
sudo dnf upgrade siyuan 2>/dev/null || \
sudo yum update siyuan

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

# 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-2026-34449 in b3log siyuan?

Review vendor-specific security notices and update b3log siyuan 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-2026-34449?

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-2026-34449?

CVE-2026-34449 is classified with a CVSS 3.1 Base Score of 9.6 (CRITICAL). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
9.6
CRITICAL SEVERITY
CVE ID CVE-2026-34449
Weakness CWE-942
Vendor b3log
Product siyuan
Published 2026-03-31
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H