CVE-2015-4277 in ASR 9000
Summary
by MITRE
The global-configuration implementation on Cisco ASR 9000 devices with software 5.1.3 and 5.3.0 improperly closes vty sessions after a commit/end operation, which allows local users to cause a denial of service (tmp/*config file creation, memory consumption, and device hang) via unspecified vectors, aka Bug ID CSCut93842.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability identified as CVE-2015-4277 affects Cisco ASR 9000 series devices operating with software versions 5.1.3 and 5.3.0, representing a critical flaw in the global configuration implementation that directly impacts device stability and availability. This issue manifests through improper handling of vty sessions following commit and end operations, creating a pathway for local attackers to exploit the device's configuration management system. The vulnerability operates at the system level where the device fails to properly terminate virtual terminal line sessions, leading to resource exhaustion and operational degradation.
The technical flaw stems from inadequate session management within the device's configuration subsystem where vty sessions are not correctly closed after configuration changes are committed and ended. This improper session termination results in persistent file handles and memory allocations that accumulate over time, ultimately consuming available system resources. The vulnerability specifically targets the temporary configuration file creation process in the tmp directory, where multiple temporary files are generated but not properly cleaned up, leading to disk space exhaustion and subsequent device hang conditions. The root cause aligns with CWE-404, which addresses improper resource cleanup, and CWE-775, which covers missing file handle closure.
The operational impact of this vulnerability extends beyond simple denial of service to encompass complete device operational failure and potential network disruption. Local users can exploit this weakness to create multiple temporary configuration files that consume disk space and memory resources, causing the device to become unresponsive and requiring manual intervention for recovery. The device hang condition represents a severe availability issue that could affect critical network infrastructure, particularly in environments where ASR 9000 devices serve as core routing platforms. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1499, which covers network denial of service attacks, and T1070, covering indicator removal on host.
Mitigation strategies for CVE-2015-4277 should focus on immediate software updates to address the configuration handling flaw, with Cisco releasing patches specifically designed to correct the improper vty session closure behavior. Network administrators should implement monitoring protocols to detect unusual temporary file creation patterns and memory consumption spikes that could indicate exploitation attempts. Additionally, implementing access controls to limit local administrative privileges and regularly reviewing configuration management processes can help reduce the attack surface. The vulnerability highlights the importance of proper resource management in network device firmware and underscores the need for comprehensive testing of configuration change operations to prevent similar issues in other network equipment. Organizations should also consider implementing automated backup and recovery procedures to minimize downtime in case of exploitation, as the device hang condition requires manual intervention to restore normal operation.