Unveiling Authentication Bypass Vulnerabilities: A Deep Dive into CWE-294 and CVE-2024-3596

In the ever-evolving landscape of cybersecurity, two critical vulnerabilities have recently come to light, shaking the foundations of authentication mechanisms. These vulnerabilities, if left unaddressed, can open the door to unauthorized access, potentially compromising sensitive systems.

• CWE-294: Authentication Bypass by Capture-replay vulnerability
  Imagine a scenario where an attacker intercepts and replays legitimate authentication data. This flaw, categorized under Common Weakness Enumeration (CWE) as CWE-294, allows malevolent actors to bypass authentication controls. The consequences? Unauthorized entry into critical systems.
  We’ll dissect the inner workings of this vulnerability, exploring its underlying design flaws and the implications it poses for security professionals.
  
  
• CVE-2024-3596 RADIUS Protocol Spoofing Vulnerability
  The Remote Authentication Dial-In User Service (RADIUS) protocol is widely used for network access authentication. However, CVE-2024-3596 exposes a weakness—a vulnerability that could be exploited to spoof RADIUS messages. In simpler terms, an attacker could impersonate a legitimate user or device.
  Our investigation will delve into the specifics of this vulnerability, shedding light on its potential impact and the steps organizations can take to mitigate the risk.

Why Should You Care?

These vulnerabilities aren’t mere technical jargon—they have real-world implications. Especially concerning are Operational Technology (OT) networks, where PLCs (Programmable Logic Controllers) and SCADA (Supervisory Control and Data Acquisition) systems reside. A successful attack could disrupt critical infrastructure, compromise safety, and lead to financial losses.

In the upcoming sections, we’ll explore these vulnerabilities in detail, dissect their anatomy, and provide actionable guidance on safeguarding your systems.

CWE-294: Authentication Bypass by Capture-replay vulnerability

• What Is It?

• • A capture-replay flaw occurs when the design of a product allows a malicious user to sniff network traffic and then bypass authentication by replaying captured messages to the server. Essentially, they mimic the original communication (sometimes with minor alterations) to gain unauthorized access.
  • Imagine an attacker eavesdropping on valid authentication messages, recording them, and then cleverly replaying those messages to trick the server into granting access.
    
    

• Common Consequences
  
  • The impact of this vulnerability lies in access control. By exploiting capture-replay, an attacker gains access to resources that would otherwise be protected by proper authentication mechanisms.
  • Think of it as someone sneaking into a secure building by copying the access card of an authorized employee.
    
    

• Mitigation Strategies
  During the architecture and design phase, consider implementing:
  
  • Sequence or time stamping functionality: This ensures that messages can be parsed only once, preventing replay attacks.
  • Message signing with cryptography: By signing messages, you prevent attackers from tampering with sequence numbers along with content.
    
    

• Real-World Examples
  In Modbus controllers, an authenticated Modbus session could be hijacked, leading to unauthorized execution of Modbus functions.

CVE-2024-3596 RADIUS Protocol Spoofing Vulnerability

• Vulnerability Summary

• • CVE-2024-3596 affects the RADIUS (Remote Authentication Dial-In User Service) protocol as defined in RFC 2865.
  • The vulnerability allows an on-path attacker (someone who can intercept and manipulate network traffic) to modify valid RADIUS responses (such as Access-Accept, Access-Reject, or Access-Challenge messages) and transform them into other responses.
  • The attack leverages a chosen-prefix collision attack against the MD5 Response Authenticator signature.
    
    

• What Does This Mean?
  
  • Imagine an attacker sitting on the communication path between a RADIUS client (e.g., a network access server) and a RADIUS server.
  • When legitimate RADIUS responses are exchanged, the attacker can tamper with them, potentially granting or denying access to network resources.
  • The vulnerability specifically targets the MD5-based authentication used in RADIUS.
    
    

• Why Is This Significant?
  
  • RADIUS is widely used for network access authentication (think VPNs).
  • If an attacker successfully exploits this vulnerability, they could impersonate users, manipulate access control decisions, or disrupt network services.
    
    

• Mitigation
  Organizations should consider:
  
  • Transitioning away from MD5: Given MD5’s known weaknesses, consider using stronger cryptographic algorithms for RADIUS authentication.
  • Monitoring network traffic: Detect any suspicious modifications to RADIUS responses.
  • Applying patches or updates: Keep RADIUS servers and clients up to date.
    
    

• Real-World Impact
  
  • While the vulnerability was disclosed in July 2024, it’s essential to stay vigilant. Security researchers and vendors are actively addressing this issue.
  • So, if you’re managing RADIUS infrastructure, keep an eye out for updates and take necessary precautions.

Conclusion

In the world of OT, vulnerabilities like CWE-294 and CVE-2024-3596 matter. RADIUS, a common authentication protocol, faces a risk due to its reliance on MD5-based authentication. In IT network traffic encryption is the norm and organizations are moving away from RADIUS authentication. However in OT, RADIUS and open traffic communication are widely used making them more vulnerable to these types of attacks.

The Path Forward: Vigilance and Adaptation As we bid farewell to these vulnerabilities, remember that security is a perpetual journey. Threats evolve, and so must our defenses. Stay informed, collaborate with the community, and adapt swiftly.

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Author: Vinny Sagar, Solution Architect, swIDch

With over 15 years of experience in pre-sales, consulting and software development in the Identity and Cyber Security space Vinny has helped many clients across various industries and regions to design and deploy Zero Trust solutions that meet their specific needs and challenges.