HIGH CVSS 7.7
Published: 2021-04-16

CVE-2021-26073

atlassian connect_express Security Advisory (CVE-2021-26073)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2021-26073 impacting atlassian connect_express. Evaluated with CVSS Base Score of 7.7 (HIGH).

Original NVD Description

Source: NIST NVD
Broken Authentication in Atlassian Connect Express (ACE) from version 3.0.2 before version 6.6.0: Atlassian Connect Express is a Node.js package for building Atlassian Connect apps. Authentication between Atlassian products and the Atlassian Connect Express app occurs with a server-to-server JWT or a context JWT. Atlassian Connect Express versions from 3.0.2 before 6.6.0 erroneously accept context JWTs in lifecycle endpoints (such as installation) where only server-to-server JWTs should be accepted, permitting an attacker to send authenticated re-installation events to an app.

📊 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
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
High (I:H)
Total modification of target system
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product atlassian / connect_express
Affected Versions *
Weakness Enumeration CWE-287

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-2021-26073 impacting atlassian connect_express.

⚡ Nuclei Detection Template (YAML) cve-2021-26073.yaml
id: cve-2021-26073

info:
  name: atlassian connect_express - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2021-26073 affecting atlassian connect_express.
    Evaluation: Broken Authentication in Atlassian Connect Express (ACE) from version 3.0.2 before version 6.6.0: Atlassian Connect Express is a Node.js package for b...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2021-26073
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
    cvss-score: 7.7
    cve-id: CVE-2021-26073
    cwe-id: CWE-287
  tags: cve,cve-2021-26073,atlassian,connect_express,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "connect_express"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2021-26073.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2021-26073
# Target: atlassian connect_express | CVSS: 7.7 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2021-26073 (atlassian connect_express)...")
    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 atlassian connect_express 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-2021-26073.sh
# Recommended Remediation & Patching Commands for CVE-2021-26073
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install connect_express 2>/dev/null || \
sudo dnf upgrade connect_express 2>/dev/null || \
sudo yum update connect_express

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

# 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-2021-26073 in atlassian connect_express?

Review vendor-specific security notices and update atlassian connect_express 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-2021-26073?

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-2021-26073?

CVE-2021-26073 is classified with a CVSS 3.1 Base Score of 7.7 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.7
HIGH SEVERITY
CVE ID CVE-2021-26073
Weakness CWE-287
Vendor atlassian
Product connect_express
Published 2021-04-16
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N