CVE-2026-2698

Executive Summary

CVE-2026-2698 is an improper access control vulnerability (CWE-284) affecting an unspecified web application or service. An authenticated user can bypass authorization checks and access resources or functionality outside their intended scope. The vulnerability has a CVSS v3.1 base score of 6.5 (Medium), with a vector of AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N. This indicates a network-exploitable flaw requiring low attack complexity and low privileges, with no user interaction needed. The primary impact is confidentiality – an attacker can read sensitive data belonging to other users or administrative areas.

The EPSS score is 0.0%, suggesting no active exploitation in the wild at the time of analysis. No public proof-of-concept (PoC) code or exploit is available. The vendor and patch status remain unknown, making this a zero-day or unpatched vulnerability.

Supply Chain & Package Security

Not applicable – The vulnerability is not associated with NPM, PyPI, Go, or Ruby ecosystems.

CVSS Breakdown & Threat Level

Threat Level: Medium. The vulnerability requires authentication but allows an attacker with low privileges to escalate access horizontally or vertically. The lack of public exploits and low EPSS reduces immediate risk, but the absence of a patch makes it a persistent threat.

Deep Dive & Mechanics

The vulnerability stems from improper enforcement of access control policies. The application likely uses role-based or attribute-based access control (RBAC/ABAC) but fails to validate user permissions on server-side endpoints. An authenticated user can manipulate parameters (e.g., user ID, role, resource ID) in API requests to access data or functions belonging to other users or higher-privileged roles.

Common attack vectors:

• Insecure Direct Object Reference (IDOR): Changing a numeric ID in a URL or POST body to access another user's profile, documents, or settings.
• Missing Function-Level Access Control: Calling administrative endpoints (e.g., /admin/users) without proper role checks.
• Privilege Escalation via Token Manipulation: Modifying JWT claims or session tokens to impersonate an admin.

The vulnerability is likely present in a custom web application, API gateway, or microservice. Without specific vendor or version data, the exact mechanism remains theoretical but aligns with classic access control failures.

Vulnerable vs. Patched Code

Since no patch or source code is available, a generic example is provided.

Vulnerable Code (Python Flask example):

@app.route('/api/user/<int:user_id>')
def get_user(user_id):
    # No authorization check – any authenticated user can access any user_id
    user = db.query("SELECT * FROM users WHERE id = ?", user_id)
    return jsonify(user)

Patched Code:

@app.route('/api/user/<int:user_id>')
def get_user(user_id):
    current_user = get_jwt_identity()
    # Verify the requesting user owns the resource or has admin role
    if current_user['id'] != user_id and 'admin' not in current_user['roles']:
        abort(403)
    user = db.query("SELECT * FROM users WHERE id = ?", user_id)
    return jsonify(user)

The fix adds a server-side check comparing the authenticated user's identity with the requested resource owner, and also allows access for admin roles.

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• Valid low-privileged user credentials (e.g., user1:password123)
• Target application URL (e.g., https://target.com)

Step 1: Identify vulnerable endpoints

# Enumerate API endpoints
curl -k -X GET "https://target.com/api/users/1" -H "Authorization: Bearer <user1_token>"

Step 2: Attempt IDOR by incrementing user IDs

for i in {1..100}; do
  response=$(curl -s -o /dev/null -w "%{http_code}" -k -X GET "https://target.com/api/users/$i" -H "Authorization: Bearer <user1_token>")
  if [ "$response" == "200" ]; then
    echo "Accessible user ID: $i"
  fi
done

Step 3: Escalate to admin functions

# Try accessing admin panel
curl -k -X GET "https://target.com/admin/dashboard" -H "Authorization: Bearer <user1_token>"

Expected outcome: The attacker can read sensitive data (PII, financial records) of other users or access administrative features.

Blue Team (Defense & Detection)

Detection:

• Monitor for anomalous access patterns: a single user accessing multiple user IDs in rapid succession.
• Alert on HTTP 403 errors followed by successful 200 responses to the same endpoint.
• Log all authorization failures and correlate with user sessions.

Prevention:

• Implement server-side authorization checks for every endpoint.
• Use a centralized policy engine (e.g., Open Policy Agent).
• Enforce least privilege and regular access reviews.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2026_2698_AccessControlBypass {
    meta:
        description = "Detects access control bypass attempts for CVE-2026-2698"
        author = "Valters IT"
        date = "2025-04-10"
        severity = "medium"
    strings:
        $id_pattern = /\/api\/users\/\d+/ nocase
        $admin_path = /\/admin\// nocase
        $auth_header = "Authorization: Bearer"
    condition:
        any of ($id_pattern, $admin_path) and #auth_header > 0
}

Sigma Rule

title: CVE-2026-2698 - Improper Access Control Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2026-2698 via IDOR or privilege escalation
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem|contains: 
            - '/api/users/'
            - '/admin/'
        sc-status: 200
    filter:
        cs-username|contains: 'admin'
    condition: selection and not filter
falsepositives:
    - Legitimate admin access
    - API pagination with user IDs
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2026-2698 - Potential Access Control Bypass";
    flow:to_server,established;
    content:"GET"; http_method;
    content:"/api/users/"; http_uri;
    pcre:"/\/api\/users\/\d+/";
    sid:1000001;
    rev:1;
    metadata: severity medium, mitre_tactic T1190;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems – If the vulnerable component is identified, restrict network access to trusted users only.
2. Implement virtual patching – Use a WAF (e.g., ModSecurity) to block requests with manipulated user IDs or unauthorized admin paths.
3. Audit access logs – Review historical logs for signs of exploitation.

Long-Term Fixes:

• Apply vendor patch – Monitor vendor channels for an official fix.
• Code review – Implement server-side authorization checks for all sensitive endpoints.
• Penetration testing – Conduct thorough access control testing.
• Adopt zero-trust architecture – Enforce least privilege and continuous verification.

Workarounds:

• Disable the vulnerable feature if possible.
• Implement additional authentication factors for sensitive operations.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst
Report generated: 2025-04-10