CVE-2007-2791 in Tru64 Unix
Summary
by MITRE
Unspecified vulnerability in the Secure Shell (SSH) in HP Tru64 UNIX 5.1B-4 and 5.1B-3 allows remote attackers to identify valid users via unspecified vectors, probably related to timing attacks and AuthInteractiveFailureRandomTimeout.
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Analysis
by VulDB Data Team • 08/01/2019
The vulnerability identified as CVE-2007-2791 represents a significant security weakness in the Secure Shell implementation within HP Tru64 UNIX operating systems version 5.1B-4 and 5.1B-3. This issue falls under the category of information disclosure vulnerabilities that can be exploited by remote attackers to gain insights into system user accounts. The vulnerability specifically affects the SSH authentication mechanism and enables attackers to distinguish between valid and invalid user accounts through indirect means. This type of vulnerability is particularly concerning as it can serve as a precursor to more sophisticated attacks targeting the system's authentication infrastructure.
The technical flaw in question is associated with timing variations in the authentication response behavior of the SSH service. According to the vulnerability description, the issue likely stems from AuthInteractiveFailureRandomTimeout mechanisms that introduce measurable delays when processing authentication attempts. These timing discrepancies occur during the interactive authentication phase where the system responds differently to valid versus invalid user credentials. The random timeout component suggests that the system does not maintain consistent response times regardless of whether the username exists in the system's user database. This inconsistency creates a timing attack vector where an attacker can measure response times to infer user account validity, a technique that has been documented in various cryptographic and authentication system attacks.
The operational impact of this vulnerability extends beyond simple user enumeration, as it provides attackers with crucial information that can be leveraged in subsequent attack phases. When an attacker can determine which usernames are valid on the system, they can focus their efforts on password spraying, brute force attacks, or credential stuffing techniques against the identified valid accounts. The vulnerability essentially undermines the fundamental security principle of authentication systems by leaking information about user accounts through timing characteristics. This weakness particularly affects environments where SSH is used for remote administration and where user account management is critical to overall system security posture. The vulnerability's presence in HP Tru64 UNIX versions indicates a broader issue within legacy systems that may have been overlooked during security assessments and penetration testing phases.
Security professionals should consider this vulnerability in relation to established frameworks such as CWE-204, which specifically addresses information exposure through timing differences, and ATT&CK technique T1110.003, which covers credential guessing using timing-based attacks. The vulnerability demonstrates how seemingly minor implementation details in cryptographic protocols can create significant security weaknesses. Organizations should implement immediate mitigations including disabling interactive authentication where possible, implementing account lockout mechanisms, and monitoring for unusual authentication patterns that might indicate timing-based enumeration attempts. Additionally, upgrading to patched versions of HP Tru64 UNIX or implementing network-level controls such as rate limiting and connection monitoring can help reduce the attack surface. The vulnerability serves as a reminder of the importance of thorough security testing, particularly for authentication mechanisms where timing variations can inadvertently leak sensitive information about system state and configuration.