CVE-2015-4244 in ASR 5000
Summary
by MITRE
The boot implementation on Cisco ASR 5000 and 5500 devices with software 14.0 allows local users to execute arbitrary Linux commands by leveraging administrative privileges for storage of these commands in a Compact Flash (CF) file, aka Bug ID CSCuu75278.
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Analysis
by VulDB Data Team • 05/31/2022
The vulnerability identified as CVE-2015-4244 affects Cisco ASR 5000 and 5500 series devices operating with software version 14.0, representing a critical security flaw in the device boot implementation that enables local privilege escalation. This vulnerability specifically targets the handling of administrative commands within the Compact Flash storage system, creating a pathway for malicious actors with administrative access to execute arbitrary Linux commands on the affected platforms. The issue stems from improper validation and execution mechanisms within the boot process where commands stored in CF files are not adequately sanitized or restricted, allowing for command injection attacks that can bypass normal security controls.
The technical exploitation of this vulnerability occurs through a specific flaw in how the system processes administrative commands stored in Compact Flash memory. When administrative users perform operations that involve storing commands in CF files, the system fails to properly validate the content being written to these storage locations. This validation failure creates an environment where malicious commands can be embedded within legitimate administrative files, which are then executed during the boot process or subsequent system operations. The vulnerability is classified as a command injection issue that operates at the system level, leveraging the elevated privileges of administrative users to gain unauthorized code execution capabilities. This flaw represents a direct violation of the principle of least privilege and demonstrates inadequate input validation mechanisms within the device's boot implementation.
The operational impact of CVE-2015-4244 extends beyond simple command execution, as it provides attackers with the ability to manipulate the device's boot process and potentially compromise the entire system integrity. Local users with administrative privileges can leverage this vulnerability to execute arbitrary Linux commands that may include system modifications, data exfiltration, or the installation of persistent backdoors. The attack vector specifically targets the Compact Flash storage mechanism, which is commonly used for configuration storage and system updates, making this vulnerability particularly dangerous as it can be exploited during routine administrative operations. This weakness creates a persistent threat that can be maintained across system reboots, as the malicious commands are stored in the CF files and executed during subsequent boot cycles. The vulnerability's impact is amplified by the fact that it requires only local administrative access, which is often more readily available than remote access credentials, making it a significant concern for network security operations.
Mitigation strategies for this vulnerability should focus on immediate software updates and patch management, as Cisco has released fixes for affected devices through security advisories. Organizations should implement strict access controls to administrative accounts and ensure that only authorized personnel have the necessary privileges to modify CF files or system configurations. The implementation of file integrity monitoring systems can help detect unauthorized modifications to CF storage locations, while network segmentation can limit the potential lateral movement of attackers who might exploit this vulnerability. Security teams should also conduct comprehensive audits of administrative access logs and system configurations to identify any potential exploitation attempts. This vulnerability aligns with CWE-78, which addresses improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.004 for executing commands through Linux shell, demonstrating how local privilege escalation can lead to full system compromise. The remediation process should include thorough testing of patches in controlled environments before deployment to ensure system stability while addressing the security vulnerability.