CVE-2001-1377 in Xtradius
Summary
by MITRE
Multiple RADIUS implementations do not properly validate the Vendor-Length of the Vendor-Specific attribute, which allows remote attackers to cause a denial of service (crash) via a Vendor-Length that is less than 2.
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Analysis
by VulDB Data Team • 09/26/2025
The vulnerability described in CVE-2001-1377 represents a critical flaw in the Remote Authentication Dial-In User Service protocol implementation across multiple network authentication systems. This weakness specifically targets the Vendor-Specific attribute within RADIUS packets, where implementations fail to properly validate the Vendor-Length field that precedes vendor-specific data. The issue stems from inadequate input validation mechanisms that do not enforce minimum length requirements for this critical attribute field, creating a pathway for malicious actors to exploit the protocol's parsing logic.
The technical nature of this vulnerability places it squarely within the realm of buffer overflows and malformed data processing as classified by CWE-129, which deals with insufficient validation of length of input data. When a RADIUS client or server receives a packet containing a Vendor-Specific attribute with a Vendor-Length field set to less than 2 bytes, the parsing routine fails to properly handle this malformed input. This condition typically results in memory corruption or pointer arithmetic errors that cause the affected system to crash or become unresponsive. The vulnerability's impact is particularly severe because RADIUS servers and clients are fundamental components of network access control systems, making them prime targets for denial of service attacks that can disrupt network connectivity and authentication services.
From an operational standpoint, this vulnerability creates significant risk for organizations relying on RADIUS-based authentication systems such as those implementing wireless network access, VPN connections, or network device management. Attackers can exploit this weakness by crafting specially formatted RADIUS packets that contain malformed Vendor-Length fields, leading to service disruption across the entire network infrastructure. The attack vector is particularly dangerous because it requires minimal privileges and can be executed remotely, allowing an attacker to cause widespread network outages without requiring physical access or elevated network permissions. This vulnerability directly maps to the MITRE ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage protocol-level weaknesses to disrupt services.
The mitigation strategies for CVE-2001-1377 focus on implementing proper input validation and boundary checking within RADIUS implementations. Network administrators should ensure that all RADIUS servers and clients enforce minimum length validation for the Vendor-Length field in Vendor-Specific attributes, requiring that this field contain at least 2 bytes of data. Updates to network authentication systems should include patches that validate attribute lengths before processing vendor-specific data, preventing malformed packets from causing system crashes. Additionally, implementing network segmentation and monitoring for unusual RADIUS traffic patterns can help detect and prevent exploitation attempts. Organizations should also consider deploying intrusion detection systems that can identify malformed RADIUS packets and automatically block suspicious traffic. The vulnerability underscores the critical importance of robust input validation in network protocols, particularly those handling authentication and access control functions, as emphasized in industry best practices for secure network design and implementation.