MEDIUM CVSS 5.3
Published: 2020-11-06

CVE-2020-28327

digium certified_asterisk Security Advisory (CVE-2020-28327)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2020-28327 impacting digium certified_asterisk. Evaluated with CVSS Base Score of 5.3 (MEDIUM).

Original NVD Description

Source: NIST NVD
A res_pjsip_session crash was discovered in Asterisk Open Source 13.x before 13.37.1, 16.x before 16.14.1, 17.x before 17.8.1, and 18.x before 18.0.1. and Certified Asterisk before 16.8-cert5. Upon receiving a new SIP Invite, Asterisk did not return the created dialog locked or referenced. This caused a gap between the creation of the dialog object, and its next use by the thread that created it. Depending on some off-nominal circumstances and timing, it was possible for another thread to free said dialog in this gap. Asterisk could then crash when the dialog object, or any of its dependent objects, were dereferenced or accessed next by the initial-creation thread. Note, however, that this crash can only occur when using a connection-oriented protocol (e.g., TCP or TLS, but not UDP) for SIP transport. Also, the remote client must be authenticated, or Asterisk must be configured for anonymous calling.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
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
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product digium / certified_asterisk
Affected Versions 16.8
Weakness Enumeration CWE-404

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-2020-28327 impacting digium certified_asterisk.

⚡ Nuclei Detection Template (YAML) cve-2020-28327.yaml
id: cve-2020-28327

info:
  name: digium certified_asterisk - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2020-28327 affecting digium certified_asterisk.
    Evaluation: A res_pjsip_session crash was discovered in Asterisk Open Source 13.x before 13.37.1, 16.x before 16.14.1, 17.x before 17.8.1, and 18.x before 18.0.1....
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2020-28327
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 5.3
    cve-id: CVE-2020-28327
    cwe-id: CWE-404
  tags: cve,cve-2020-28327,digium,certified_asterisk,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "certified_asterisk"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2020-28327.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2020-28327
# Target: digium certified_asterisk | CVSS: 5.3 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2020-28327 (digium certified_asterisk)...")
    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 digium certified_asterisk scope (16.8).")
        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-2020-28327.sh
# Recommended Remediation & Patching Commands for CVE-2020-28327
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install certified_asterisk 2>/dev/null || \
sudo dnf upgrade certified_asterisk 2>/dev/null || \
sudo yum update certified_asterisk

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

# 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-2020-28327 in digium certified_asterisk?

Review vendor-specific security notices and update digium certified_asterisk 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-2020-28327?

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-2020-28327?

CVE-2020-28327 is classified with a CVSS 3.1 Base Score of 5.3 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
5.3
MEDIUM SEVERITY
CVE ID CVE-2020-28327
Weakness CWE-404
Vendor digium
Product certified_asterisk
Published 2020-11-06
Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H