Critical Cyber Security Vulnerabilities Exploited: Fortinet SSL VPN, RDP, and LDAP Hardening

The growing sophistication of cyber threats continues to put organisations at risk, with vulnerabilities being exploited faster and more aggressively than ever. In this in-depth analysis, we will explore critical vulnerabilities in Fortinet SSL VPN, Remote Desktop Protocol (RDP), and the challenges posed by LDAP hardening.

We’ll also provide actionable recommendations, mitigation strategies, and insights to help your organisation fortify its defences against these threats. If your team requires expert guidance to secure your IT environment, TechVertu’s Managed Cyber Security services can provide tailored support.

Introduction to exploited cybersecurity vulnerabilities

The evolving threat landscape

In the past decade, the rapid adoption of digital systems has outpaced the ability of many organisations to secure their environments effectively. Cybercriminals have capitalised on this gap, exploiting vulnerabilities to achieve everything from data theft to ransomware deployments.

Why vulnerabilities are targeted

Hackers target vulnerabilities because they offer:

• Direct access to sensitive data (e.g., admin credentials, user databases).
• Remote code execution (RCE) to implant malware or achieve lateral movement.
• Persistence within networks allows attackers to exploit systems over time.

In many cases, vulnerabilities are left unpatched due to a lack of awareness, misconfigured systems, or resource constraints in IT departments.

Fortinet SSL VPN vulnerabilities (CVE-2018-13379)

Technical overview of the flaw

The Fortinet SSL VPN vulnerability (CVE-2018-13379) is a critical pre-authentication path traversal flaw that affects Fortigate devices. It allows attackers to access sensitive files directly, bypassing authentication mechanisms entirely.

Key Details:

• Impact: Unauthorised access to plaintext credentials and sensitive configurations.
• Vulnerable Versions: FortiOS 6.0.0 to 6.0.4 and 5.6.3 to 5.6.7.
• CVSS Score: 9.8 (Critical).

Exploitation methods and risks

Attackers exploit this flaw using a carefully crafted URL:

https://<target-ip>/remote/fgt_lang?lang=/../../../..//////////dev/cmdb/sslvpn_websession

This URL structure allows direct access to files stored on Fortinet appliances, bypassing authentication entirely.

Real-World Risks:

• Attackers can harvest plaintext admin credentials to compromise networks further.
• Organisations using vulnerable Fortinet VPNs face exposure to ransomware, data exfiltration, and lateral movement.

Real-world attacks leveraging CVE-2018-13379

Since its disclosure, CVE-2018-13379 has been widely exploited by Advanced Persistent Threat (APT) groups, including those attributed to nation-states. High-profile ransomware gangs have also leveraged this vulnerability to deploy attacks.

Best practices for mitigating fortinet vulnerabilities

1. Update Firmware Immediately: Ensure your Fortigate devices run patched versions of FortiOS.
2. Monitor for Indicators of Compromise (IoCs): Scan logs for unauthorised file access patterns.
3. Segregate VPN Traffic: Limit VPN access to essential resources and segregate traffic using VLANs.

Remote desktop protocol (RDP) exploits (CVE-2019 series)

RDP in the modern IT environment

RDP is an essential tool for remote administration, widely used in enterprise environments. However, its ubiquity makes it a prime target for attackers.

Analysis of Dejablue (CVE-2019-1181 and CVE-2019-1182)

The Tencent security team has constructed a #POC of CVE-2019-1181/1182, which is currently stable use. #RDS #NEWBLUEKEEP #wormable
Rapid patch！
REF：https://t.co/4aYknuUb5f pic.twitter.com/CpBKeWUew4

— blackorbird (@blackorbird) August 16, 2019

DejaBlue affects multiple Windows versions, enabling pre-authentication remote code execution. Unlike BlueKeep, which targeted older systems, DejaBlue impacts modern versions such as Windows 10.

Key Details:

• Impact: Wormable exploit enabling automated spread across networks.
• CVSS Score: 9.8 (Critical).
• Target Systems: Windows 7, Windows 8.1, Windows 10, and corresponding server versions.

Comparisons to BlueKeep and their implications

While BlueKeep (CVE-2019-0708) primarily targeted legacy systems, DejaBlue’s reach across modern systems signifies a broader risk for enterprises. Unpatched systems are particularly vulnerable to ransomware attacks leveraging this exploit.

Securing RDP configurations

1. Enable Network Level Authentication (NLA): Requires credentials before session establishment.
2. Use Strong Passwords and Account Lockouts: Prevent brute-force attacks.
3. Restrict RDP Access via Firewall Rules: Allow access only from trusted IP ranges.

Ldap hardening challenges

What is LDAP, and why is it vulnerable?

LDAP is a protocol for accessing and maintaining directory services like Microsoft Active Directory. However, legacy LDAP implementations often lack security, transmitting data in plaintext.

Microsoft’s 2020 hardening policies

To address these vulnerabilities, Microsoft now mandates LDAP channel binding and signing. These changes enhance encryption and authentication but can disrupt applications relying on insecure LDAP configurations.

Steps to secure LDAP:

1. Enable Diagnostic Logging: Identify insecure LDAP binds using Event IDs 2887 and 2889.
2. Update Applications: Reconfigure software to use secure LDAP binds.
3. Deploy GPO Settings: Enforce LDAP signing and channel binding requirements.

Broader implications of unpatched vulnerabilities

Consequences for businesses:

1. Ransomware Attacks: Vulnerabilities like CVE-2018-13379 and DejaBlue are frequently used to deploy ransomware.
2. Data Breaches: Exploited vulnerabilities can lead to the exfiltration of sensitive data.
3. Financial Losses: Recovery costs from cyberattacks average £3.5 million per incident globally.

How techvertu can help secure your systems

Tailored cybersecurity solutions

Managing cybersecurity risks requires a comprehensive approach tailored to your business needs. At TechVertu, our Managed Cyber Security services provide:

• Proactive Threat Monitoring: Stay ahead of evolving cyber threats.
• Vulnerability Assessments: Identify and patch risks in your environment.
• Tailored Security Solutions: Protect your systems with bespoke defences.

Partnering with experts to achieve resilience

Addressing vulnerabilities such as Fortinet SSL VPN flaws, RDP exploits, and LDAP misconfigurations can significantly reduce your organisation’s exposure to cyber threats. Contact Techvertu today for expert guidance and managed cyber security support.