VPN Vulnerabilities Highlighted in Recent Security Research
/ 3 min read
Quick take - In 2023, research revealed that over half of enterprises using VPNs, particularly Fortinet’s solution, have faced attacks exploiting vulnerabilities, highlighting significant security concerns due to a lack of logging for successful login attempts, which could allow attackers to validate credentials undetected.
Fast Facts
- In 2023, over half of enterprises reported attacks exploiting VPN vulnerabilities, raising significant security concerns, particularly with Fortinet’s VPN solution.
- A research investigation revealed a bug in Fortinet’s VPN that allows attackers to validate credentials without detection due to a lack of logging for successful login attempts.
- The absence of logs for successful authentications hinders incident response teams from distinguishing between failed and successful brute-force attacks.
- Recommendations for improving security include enhancing logging mechanisms, implementing multi-factor authentication (MFA), and conducting regular audits of the VPN system.
- The research highlights the need for continuous vigilance and collaboration within the cybersecurity community to address emerging threats effectively.
VPN Vulnerabilities and Security Concerns in 2023
In 2023, the increasing use of virtual private networks (VPNs) by enterprises for secure remote access to sensitive data has attracted the attention of threat actors. Research indicates that over half of enterprises have experienced attacks exploiting VPN vulnerabilities, highlighting a significant security concern.
Investigation into Fortinet VPN
The research specifically focused on popular VPN clients, including Fortinet’s widely used VPN solution. During the investigation, a method was developed to automatically validate credentials against Fortinet VPN servers. This process revealed a vulnerability: a bug that could be exploited by attackers, potentially compromising organizational security. Despite being informed of the findings, Fortinet does not classify the issue as a vulnerability but acknowledges the security implications it presents.
The investigation began with efforts to create an automatic credential validation system for Fortinet VPN. Initial attempts using clients like OpenConnect proved unreliable for automation. Consequently, the research team analyzed communication protocols between the client and the VPN server, documenting interactions with tools such as Burp Suite. They discovered that a simple HTTPS request initiates the authentication attempt against the server. The server’s response provides critical information about login attempts. Successful logins generate a specific response code (ret=1), while failed attempts return a different code (ret=0).
Security Risks and Recommendations
A troubling finding was the lack of logging for successful login attempts, which was unexpected. While logs for failed attempts were available, the absence of records for successful authentications means that incident response (IR) teams are unable to distinguish between failed and successful brute-force attempts. This vulnerability allows attackers to exploit this logging gap, validating credentials without detection and potentially compromising networks.
In typical brute-force attacks, successful logins would generate log entries, enhancing visibility for security teams. However, the current system used by Fortinet does not log successful authentications, posing a significant security risk. Attackers could leverage leaked credentials to identify valid VPN users without exposing themselves.
Recommendations for improvement include enhancing Fortinet’s logging mechanisms to capture all authentication attempts at the earliest stage. To bolster security for Fortinet VPN users, experts recommend implementing multi-factor authentication (MFA) and strict monitoring of authentication logs. Regular audits and updates to the VPN system are also advised to maintain robust security. A log of “SSL tunnel shutdown” for validated users may provide a potential avenue for detecting unauthorized access attempts. Moreover, deploying a Web Application Firewall (WAF) in front of the VPN server could help identify and mitigate such attacks.
The research underscores the importance of continuous vigilance in cybersecurity to protect sensitive data. It emphasizes the necessity of collaboration within the cybersecurity community. Sharing findings and developing solutions to counter emerging threats is crucial for enhancing the overall security landscape.
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