CVE-2016-1853 in Mac OS X
Summary
by MITRE
Tcl in Apple OS X before 10.11.5 allows remote attackers to obtain sensitive information by leveraging SSLv2 support.
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Analysis
by VulDB Data Team • 11/07/2024
The vulnerability identified as CVE-2016-1853 affects Tcl implementations within Apple macOS versions prior to 10.11.5, representing a significant security weakness that stems from the inclusion of deprecated SSLv2 protocol support. This flaw exists within the Tcl scripting language environment that is embedded in Apple's operating system, creating a potential attack vector for remote threat actors who wish to extract sensitive information from systems running vulnerable versions of macOS. The vulnerability specifically exploits the presence of SSLv2 support within the Tcl implementation, which was historically considered insecure and deprecated by industry standards. The inclusion of this outdated protocol support creates an attack surface that can be leveraged by adversaries to gain unauthorized access to system information, particularly when Tcl applications are configured to use SSL connections for data transmission or authentication processes.
The technical mechanism behind this vulnerability involves the improper handling of SSLv2 connections within the Tcl networking libraries of macOS. When applications utilizing Tcl attempt to establish secure connections through SSLv2, the implementation fails to properly validate or sanitize the connection parameters, allowing attackers to manipulate the SSL handshake process. This weakness enables attackers to potentially intercept or extract sensitive data that would normally be protected by secure communication channels. The vulnerability manifests because the Tcl implementation does not adequately enforce security policies or validate the cryptographic parameters used in SSLv2 connections, creating opportunities for information disclosure attacks. According to CWE-310, this represents a cryptographic vulnerability related to improper use of cryptographic protocols, specifically involving the use of weak or deprecated cryptographic standards that should never be employed in modern security implementations.
The operational impact of CVE-2016-1853 extends beyond simple information disclosure, as it undermines the fundamental security assumptions of applications relying on Tcl for network communications. Systems running affected macOS versions become vulnerable to man-in-the-middle attacks where attackers can intercept communications between Tcl-based applications and remote servers, potentially accessing authentication credentials, session tokens, or other sensitive data transmitted through the insecure SSLv2 connections. This vulnerability affects any application that utilizes Tcl's SSL networking capabilities, including web applications, network management tools, and system administration scripts that depend on secure communications. The risk is particularly elevated in enterprise environments where Tcl applications may be used for critical system operations or automated tasks that require secure network connections. Attackers can exploit this vulnerability without requiring local system access, making it a significant concern for organizations that deploy Tcl-based solutions in their infrastructure.
Mitigation strategies for CVE-2016-1853 primarily focus on updating to Apple macOS 10.11.5 or later versions, which removes the deprecated SSLv2 support from the Tcl implementation. Organizations should also implement network monitoring to detect and block SSLv2 traffic patterns, as well as review all Tcl-based applications to ensure they are not configured to use deprecated cryptographic protocols. Security teams should consider implementing application whitelisting policies to prevent execution of vulnerable Tcl scripts and conduct comprehensive vulnerability assessments of all systems running affected macOS versions. The remediation process should include thorough testing of updated systems to ensure that the removal of SSLv2 support does not break existing applications that may have been inadvertently relying on this deprecated functionality. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and defense evasion, as attackers can use it to extract sensitive information while potentially avoiding detection through the use of deprecated protocols that are less commonly monitored. Organizations should also implement security awareness training to help prevent accidental configuration of applications to use insecure cryptographic protocols.