MEDIUM CVSS 4.6
Published: 2026-04-13

CVE-2026-33657

espocrm espocrm Security Advisory (CVE-2026-33657)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-33657 impacting espocrm espocrm. Evaluated with CVSS Base Score of 4.6 (MEDIUM).

Original NVD Description

Source: NIST NVD
EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have a stored HTML injection vulnerability that allows any authenticated user with standard (non-administrative) privileges to inject arbitrary HTML into system-generated email notifications by crafting malicious content in the post field of stream activity notes. The vulnerability exists because server-side Handlebars templates render the post field using unescaped triple-brace syntax, the Markdown processor preserves inline HTML by default, and the rendering pipeline explicitly skips sanitization for fields present in additionalData, creating a path where attacker-controlled HTML is accepted, stored, and rendered directly into emails without any escaping. Since the emails are sent using the system's configured SMTP identity (such as an administrative sender address), the injected content appears fully trusted to recipients, enabling phishing attacks, user tracking via embedded resources like image beacons, and UI manipulation within email content. The @mention feature further increases the impact by allowing targeted delivery of malicious emails to specific users. This issue has been fixed in version 9.3.4.

📊 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
Unchanged (S:U)
Confined to same security context
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 espocrm / espocrm
Affected Versions *
Weakness Enumeration CWE-80

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-2026-33657 impacting espocrm espocrm.

⚡ Nuclei Detection Template (YAML) cve-2026-33657.yaml
id: cve-2026-33657

info:
  name: espocrm espocrm - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-33657 affecting espocrm espocrm.
    Evaluation: EspoCRM is an open source customer relationship management application. Versions 9.3.3 and below have a stored HTML injection vulnerability that allow...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-33657
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
    cvss-score: 4.6
    cve-id: CVE-2026-33657
    cwe-id: CWE-80
  tags: cve,cve-2026-33657,espocrm,espocrm,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "espocrm"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-33657.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-33657
# Target: espocrm espocrm | CVSS: 4.6 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-33657 (espocrm espocrm)...")
    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 espocrm espocrm 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-2026-33657.sh
# Recommended Remediation & Patching Commands for CVE-2026-33657
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install espocrm 2>/dev/null || \
sudo dnf upgrade espocrm 2>/dev/null || \
sudo yum update espocrm

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

# 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-2026-33657 in espocrm espocrm?

Review vendor-specific security notices and update espocrm espocrm 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-2026-33657?

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-2026-33657?

CVE-2026-33657 is classified with a CVSS 3.1 Base Score of 4.6 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
4.6
MEDIUM SEVERITY
CVE ID CVE-2026-33657
Weakness CWE-80
Vendor espocrm
Product espocrm
Published 2026-04-13
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N