HIGH CVSS 7.1
Published: 2026-03-10

CVE-2026-30926

b3log siyuan Security Advisory (CVE-2026-30926)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-30926 impacting b3log siyuan. Evaluated with CVSS Base Score of 7.1 (HIGH).

Original NVD Description

Source: NIST NVD
SiYuan is a personal knowledge management system. Prior to 3.5.10, a privilege escalation vulnerability exists in the publish service of SiYuan Note that allows low-privilege publish accounts (RoleReader) to modify notebook content via the /api/block/appendHeadingChildren API endpoint. The endpoint requires only the model.CheckAuth role, which accepts RoleReader sessions, but it does not enforce stricter checks, such as CheckAdminRole or CheckReadonly. This allows remote authenticated publish users with read-only privileges to append new blocks to existing documents, compromising the integrity of stored notes.

📊 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
Low (PR:L)
Standard user access required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
Low (C:L)
Partial information leakage
Integrity
High (I:H)
Total modification of target system
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product b3log / siyuan
Affected Versions *
Weakness Enumeration CWE-284

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-2026-30926 impacting b3log siyuan.

⚡ Nuclei Detection Template (YAML) cve-2026-30926.yaml
id: cve-2026-30926

info:
  name: b3log siyuan - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-30926 affecting b3log siyuan.
    Evaluation: SiYuan is a personal knowledge management system. Prior to 3.5.10, a privilege escalation vulnerability exists in the publish service of SiYuan Note t...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-30926
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
    cvss-score: 7.1
    cve-id: CVE-2026-30926
    cwe-id: CWE-284
  tags: cve,cve-2026-30926,b3log,siyuan,high

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-2026-30926.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-30926
# Target: b3log siyuan | CVSS: 7.1 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-30926 (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-2026-30926.sh
# Recommended Remediation & Patching Commands for CVE-2026-30926
# 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.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-30926 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-2026-30926?

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-2026-30926?

CVE-2026-30926 is classified with a CVSS 3.1 Base Score of 7.1 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.1
HIGH SEVERITY
CVE ID CVE-2026-30926
Weakness CWE-284
Vendor b3log
Product siyuan
Published 2026-03-10
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N