MEDIUM CVSS 6.1
Published: 2026-03-11

CVE-2026-31859

craftcms craft_cms Security Advisory (CVE-2026-31859)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-31859 impacting craftcms craft_cms. Evaluated with CVSS Base Score of 6.1 (MEDIUM).

Original NVD Description

Source: NIST NVD
Craft is a content management system (CMS). The fix for CVE-2025-35939 in craftcms/cms introduced a strip_tags() call in src/web/User.php to sanitize return URLs before they are stored in the session. However, strip_tags() only removes HTML tags (angle brackets) -- it does not inspect or filter URL schemes. Payloads like javascript:alert(document.cookie) contain no HTML tags and pass through strip_tags() completely unmodified, enabling reflected XSS when the return URL is rendered in an href attribute. This vulnerability is fixed in 5.9.7 and 4.17.3.

📊 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
Low (C:L)
Partial information leakage
Integrity
Low (I:L)
Partial data modification possible
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product craftcms / craft_cms
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-2026-31859 impacting craftcms craft_cms.

⚡ Nuclei Detection Template (YAML) cve-2026-31859.yaml
id: cve-2026-31859

info:
  name: craftcms craft_cms - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-31859 affecting craftcms craft_cms.
    Evaluation: Craft is a content management system (CMS). The fix for CVE-2025-35939 in craftcms/cms introduced a strip_tags() call in src/web/User.php to sanitize ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-31859
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2026-31859
    cwe-id: CWE-79
  tags: cve,cve-2026-31859,craftcms,craft_cms,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "craft_cms"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-31859.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-31859
# Target: craftcms craft_cms | CVSS: 6.1 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-31859 (craftcms craft_cms)...")
    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 craftcms craft_cms 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-2026-31859.sh
# Recommended Remediation & Patching Commands for CVE-2026-31859
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install craft_cms 2>/dev/null || \
sudo dnf upgrade craft_cms 2>/dev/null || \
sudo yum update craft_cms

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

# 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-2026-31859 in craftcms craft_cms?

Review vendor-specific security notices and update craftcms craft_cms 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-2026-31859?

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-2026-31859?

CVE-2026-31859 is classified with a CVSS 3.1 Base Score of 6.1 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
6.1
MEDIUM SEVERITY
CVE ID CVE-2026-31859
Weakness CWE-79
Vendor craftcms
Product craft_cms
Published 2026-03-11
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N