CVE-2005-2359 in FreeBSD
Summary
by MITRE
The AES-XCBC-MAC algorithm in IPsec in FreeBSD 5.3 and 5.4, when used for authentication without other encryption, uses a constant key instead of the one that was assigned by the system administrator, which can allow remote attackers to spoof packets to establish an IPsec session.
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Analysis
by VulDB Data Team • 03/11/2021
The vulnerability described in CVE-2005-2359 represents a critical weakness in the IPsec implementation of FreeBSD versions 5.3 and 5.4, specifically affecting the AES-XCBC-MAC algorithm used for packet authentication. This flaw resides in the cryptographic subsystem where the system fails to properly utilize administrator-configured keys for authentication purposes, instead defaulting to a hardcoded constant key value. The issue fundamentally undermines the integrity and authenticity guarantees that IPsec is designed to provide, creating a pathway for malicious actors to manipulate network traffic without detection.
The technical implementation flaw occurs within the IPsec framework's authentication mechanism where the AES-XCBC-MAC algorithm is employed to verify packet integrity and authenticity. When IPsec operates in authentication-only mode without encryption, the system should utilize keys specifically configured by system administrators to ensure proper cryptographic separation and security. However, the FreeBSD implementation contains a coding error that causes the system to ignore these configured keys and instead apply a static, predictable key value. This constant key vulnerability stems from improper key management within the cryptographic module and represents a clear violation of secure cryptographic practices as outlined in industry standards such as CWE-327, which addresses the use of weak or predictable cryptographic keys.
The operational impact of this vulnerability is severe and directly enables man-in-the-middle attacks against IPsec sessions. Remote attackers can exploit this weakness to forge authentication tags that will be accepted by the receiving system, allowing them to inject malicious packets into IPsec tunnels without being detected. The attack vector is particularly dangerous because it requires no local access or authentication credentials, making it a passive attack that can be executed from anywhere on the network. This vulnerability essentially renders the authentication component of IPsec ineffective, potentially allowing attackers to establish unauthorized IPsec sessions, redirect traffic, or perform session hijacking operations that compromise the entire network security posture.
The vulnerability aligns with several ATT&CK framework techniques including T1046 for network service scanning and T1566 for credential harvesting, as attackers can leverage the predictable key to bypass authentication mechanisms. Organizations using affected FreeBSD versions face significant risk of unauthorized network access and data compromise, particularly in environments where IPsec is used for securing sensitive communications. The attack surface is further expanded because IPsec is commonly deployed in enterprise networks, VPN implementations, and secure communication channels where the integrity of network traffic is paramount. System administrators should immediately implement mitigations including upgrading to patched FreeBSD versions, implementing additional network monitoring, and potentially disabling the affected authentication mode until proper patches are applied.
This vulnerability demonstrates the critical importance of proper key management in cryptographic systems and the potential consequences of hardcoded values in security-sensitive components. The flaw represents a failure in the principle of least privilege and proper cryptographic key handling, where the system should never rely on static keys for authentication purposes. Organizations should conduct immediate vulnerability assessments to identify any systems running affected FreeBSD versions and ensure all IPsec configurations are properly validated. The incident underscores the necessity of thorough code review processes for cryptographic implementations and highlights the importance of maintaining up-to-date security patches in network infrastructure components.