HIGH CVSS 8.7
Published: 2026-04-13

CVE-2026-23891

decidim decidim Security Advisory (CVE-2026-23891)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-23891 impacting decidim decidim. Evaluated with CVSS Base Score of 8.7 (HIGH).

Original NVD Description

Source: NIST NVD
Decidim is a participatory democracy framework. In versions below 0.30.5 and 0.31.0.rc1 through 0.31.0, a stored code execution vulnerability in the user name field allows a low-privileged attacker to execute arbitrary code in the context of any user who passively visits a comment page, resulting in high confidentiality and integrity impact across security boundaries. This issue has been fixed in versions 0.30.5 and 0.31.1.

📊 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
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
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product decidim / decidim
Affected Versions *
Weakness Enumeration CWE-79

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-2026-23891 impacting decidim decidim.

⚡ Nuclei Detection Template (YAML) cve-2026-23891.yaml
id: cve-2026-23891

info:
  name: decidim decidim - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-23891 affecting decidim decidim.
    Evaluation: Decidim is a participatory democracy framework. In versions below 0.30.5 and 0.31.0.rc1 through 0.31.0, a stored code execution vulnerability in the u...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-23891
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
    cvss-score: 8.7
    cve-id: CVE-2026-23891
    cwe-id: CWE-79
  tags: cve,cve-2026-23891,decidim,decidim,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "decidim"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-23891.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-23891
# Target: decidim decidim | CVSS: 8.7 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-23891 (decidim decidim)...")
    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 decidim decidim 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-2026-23891.sh
# Recommended Remediation & Patching Commands for CVE-2026-23891
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install decidim 2>/dev/null || \
sudo dnf upgrade decidim 2>/dev/null || \
sudo yum update decidim

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

# 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

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-23891 in decidim decidim?

Review vendor-specific security notices and update decidim decidim 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-2026-23891?

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-2026-23891?

CVE-2026-23891 is classified with a CVSS 3.1 Base Score of 8.7 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
8.7
HIGH SEVERITY
CVE ID CVE-2026-23891
Weakness CWE-79
Vendor decidim
Product decidim
Published 2026-04-13
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N