CVE-1999-1098 in BSD
Summary
by MITRE
vulnerability in bsd telnet client with encryption and kerberos 4 authentication allows remote attackers to decrypt the session via sniffing.
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Analysis
by VulDB Data Team • 04/03/2025
The vulnerability identified as CVE-1999-1098 represents a critical security flaw in the bsd telnet client implementation that specifically affects systems utilizing both encryption and kerberos 4 authentication mechanisms. This weakness stems from improper handling of cryptographic operations within the telnet protocol stack, creating a scenario where malicious actors can potentially intercept and decrypt network traffic between client and server components. The vulnerability primarily impacts environments where telnet services are configured with encryption and kerberos 4 authentication, which were common in enterprise networks during the late 1990s and early 2000s.
The technical root cause of this vulnerability lies in the flawed implementation of the telnet encryption protocol within the bsd telnet client software. When kerberos 4 authentication is enabled alongside encryption, the client fails to properly secure the cryptographic keys or session data, allowing an attacker positioned on the network to perform packet sniffing operations and subsequently decrypt the transmitted information. This weakness specifically manifests in the way the client handles the key exchange process and session management, creating predictable cryptographic states that can be exploited through passive network monitoring. The flaw operates at the application layer of the network stack and affects the integrity of the encryption implementation rather than the authentication mechanism itself.
The operational impact of CVE-1999-1098 is significant as it undermines the fundamental security assumptions of encrypted telnet communications. Attackers can exploit this vulnerability to gain unauthorized access to sensitive information transmitted through telnet sessions, including user credentials, system commands, and confidential data exchanges. The vulnerability essentially nullifies the encryption protection that administrators implement to secure remote access sessions, making it particularly dangerous in environments where telnet is used for administrative tasks. Organizations using affected systems face potential data breaches, unauthorized system access, and compromise of privileged accounts that rely on telnet for remote management.
Mitigation strategies for this vulnerability require immediate implementation of security patches provided by the software vendors, along with comprehensive network security measures to prevent unauthorized packet interception. System administrators should consider disabling telnet services in favor of more secure alternatives such as ssh protocols, which provide robust encryption and authentication mechanisms. Network segmentation and intrusion detection systems can help detect and prevent exploitation attempts, while regular security audits should verify that no systems remain vulnerable to this specific flaw. This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in software implementations, and corresponds to techniques listed in the ATT&CK framework under credential access and defense evasion tactics, highlighting the need for comprehensive security remediation across both network and application layers.