CVE-2016-3099 in Enterprise Linux Desktop
Summary
by MITRE
mod_ns in Red Hat Enterprise Linux Desktop 7, Red Hat Enterprise Linux HPC Node 7, Red Hat Enterprise Linux Server 7, and Red Hat Enterprise Linux Workstation 7 allows remote attackers to force the use of ciphers that were not intended to be enabled.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2016-3099 affects the mod_ns module in Red Hat Enterprise Linux versions 7 across multiple product lines including Desktop, HPC Node, Server, and Workstation. This issue represents a significant cryptographic weakness that undermines the security posture of affected systems by allowing unauthorized parties to manipulate cipher suite selection during TLS connections. The vulnerability resides within the mod_ns module which is part of the Apache HTTP Server configuration for Red Hat Enterprise Linux environments.
The technical flaw stems from improper handling of cipher suite configuration within the mod_ns module, specifically allowing remote attackers to override the intended cipher preferences and force the use of weaker or deprecated cryptographic algorithms. This occurs through manipulation of the SSL configuration parameters that control which ciphers are acceptable for secure connections. The vulnerability enables what is known as a cipher suite downgrade attack, where attackers can force connections to use less secure encryption methods that were explicitly disabled or not intended for use.
From an operational perspective, this vulnerability creates substantial risk for organizations relying on Red Hat Enterprise Linux servers for secure communications. Attackers can exploit this weakness to perform man-in-the-middle attacks, potentially intercepting and modifying sensitive data transmitted over HTTPS connections. The impact extends beyond simple data confidentiality breaches as it can enable more sophisticated attacks including session hijacking, credential theft, and complete compromise of secure web applications. The vulnerability affects systems where mod_ns is actively configured and used, particularly in environments handling sensitive information such as financial transactions, personal data, or confidential business communications.
The security implications align with CWE-327, which addresses the use of weak cryptographic algorithms, and represents a direct violation of secure configuration practices. Organizations should consider this vulnerability in the context of ATT&CK technique T1566, which covers credential harvesting through phishing and network attacks. The most effective mitigations include immediate patching of affected Red Hat Enterprise Linux systems, implementation of strict cipher suite restrictions in Apache configuration files, and deployment of automated monitoring solutions to detect unauthorized cipher suite changes. Additionally, organizations should conduct comprehensive security assessments to identify all instances of mod_ns usage and ensure that cryptographic configurations are properly enforced across all web servers. The vulnerability highlights the importance of proper cryptographic protocol implementation and the necessity of maintaining up-to-date security patches across enterprise environments.