CVE-2017-13684 in Libra 64xx
Summary
by MITRE
Unisys Libra 64xx and 84xx and FS601 class systems with MCP-FIRMWARE before 43.211 allow remote authenticated users to cause a denial of service (program crash) or have unspecified other impact via vectors related to incorrect literal handling, which trigger CPM stack corruption.
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Analysis
by VulDB Data Team • 11/20/2019
The vulnerability identified as CVE-2017-13684 affects Unisys Libra 64xx and 84xx systems along with FS601 class systems that utilize MCP-FIRMWARE versions prior to 43.211. This represents a critical security flaw that demonstrates how improper handling of literal values within the system's firmware can lead to severe operational consequences. The affected systems operate within enterprise computing environments where reliability and continuous operation are paramount, making this vulnerability particularly dangerous as it can disrupt mission-critical operations.
The technical root cause of this vulnerability lies in incorrect literal handling mechanisms within the MCP-FIRMWARE implementation. When authenticated remote users interact with the system using specific vectors related to literal processing, the firmware fails to properly validate or manage these inputs, resulting in corruption of the CPM stack. This stack corruption represents a fundamental failure in memory management and program execution flow. The CWE-121 category applies here as the vulnerability involves stack-based buffer overflow conditions that occur due to improper handling of data types and literal values during program execution.
From an operational perspective, this vulnerability presents multiple attack vectors that can be exploited by authenticated remote adversaries. The impact includes potential denial of service conditions where system programs may crash and require manual intervention to restore functionality. Beyond immediate service disruption, the unspecified other impacts suggest potential for more severe consequences including data corruption, unauthorized access to system resources, or escalation of privileges. The attack requires only authenticated access, which means that insiders or attackers who have gained legitimate credentials could exploit this weakness without requiring additional privilege escalation techniques.
The vulnerability's exploitation demonstrates weaknesses in input validation and memory management within legacy mainframe systems. Systems utilizing this firmware architecture are particularly susceptible because they process complex computational operations that require precise stack management and literal value handling. The fact that this affects multiple system classes within the Unisys Libra family indicates a systemic design flaw rather than an isolated incident, suggesting that organizations with multiple affected systems face widespread risk.
Organizations should implement immediate mitigations including firmware updates to MCP-FIRMWARE version 43.211 or higher to address the root cause of the vulnerability. Network segmentation and access controls should be reinforced to limit the number of authenticated users who can reach affected systems. Regular security assessments should include verification of firmware versions and monitoring for unusual system behavior that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service techniques, highlighting the need for comprehensive security monitoring and incident response procedures. Additionally, system administrators should implement regular patch management processes to ensure all legacy systems receive timely security updates and maintain operational integrity against similar vulnerabilities.