CVE-2001-1475 in SSH
Summary
by MITRE
SSH before 2.0, when using RC4 and password authentication, allows remote attackers to replay messages until a new server key (VK) is generated.
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Analysis
by VulDB Data Team • 11/17/2024
The vulnerability described in CVE-2001-1475 represents a significant security flaw in early Secure Shell implementations that affected SSH versions prior to 2.0. This weakness specifically manifests when the SSH protocol employs RC4 encryption cipher combined with password-based authentication methods, creating a window of opportunity for malicious actors to exploit the communication channel. The vulnerability stems from the protocol's handling of message replay mechanisms and key management processes, particularly in scenarios where server keys are regenerated periodically.
The technical implementation flaw resides in the message authentication and replay protection mechanisms within the SSH protocol stack. When RC4 encryption is utilized alongside password authentication, the system fails to properly validate message sequences or maintain adequate state tracking between client and server communications. This allows attackers to capture and replay valid protocol messages without immediate detection, effectively enabling them to manipulate the authentication flow until the server generates a new server key. The underlying issue is particularly concerning because it exploits fundamental assumptions about message integrity and session state management within the SSH protocol implementation.
The operational impact of this vulnerability extends beyond simple authentication bypasses, creating potential for extended session manipulation and unauthorized access to systems. Attackers can leverage this weakness to perform prolonged exploitation attempts, potentially gaining unauthorized access to sensitive systems and data repositories. The vulnerability particularly affects environments where SSH is used for remote administration, file transfers, and secure communications, making it a critical concern for network security administrators. Organizations relying on older SSH implementations face significant risk exposure, especially in scenarios involving privileged access or sensitive data handling.
Mitigation strategies for this vulnerability require immediate implementation of security patches and protocol updates to address the specific message replay handling issues. System administrators should upgrade to SSH 2.0 or later versions that properly implement key management and message authentication mechanisms. The recommended approach includes disabling RC4 cipher suites in favor of more secure encryption algorithms such as AES or 3DES, while also implementing proper session monitoring and key rotation policies. Additionally, organizations should consider implementing network-level controls such as intrusion detection systems to monitor for suspicious replay patterns and establish robust audit trails for authentication events.
This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in authentication protocols, and demonstrates characteristics consistent with ATT&CK technique T1566 related to credential access through network protocols. The issue highlights the importance of proper cryptographic protocol implementation and the necessity of robust key management practices in secure communication systems. Security professionals should note that this vulnerability represents an early example of how flawed protocol state management can create persistent security weaknesses that may remain undetected for extended periods.