Cisco ASA CLI Command Injection and Privilege Escalation Vulnerability (CVE-2016-6367, EPICBANANA)

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2016-6367, widely known as 'EPICBANANA') exists in the Command Line Interface (CLI) parser of Cisco Adaptive Security Appliance (ASA), PIX, and FWSM software. Due to insufficient validation of input parameters within specific CLI commands, the parser fails to handle invalid inputs correctly, leading to memory corruption or command injection. This allows an attacker with local access to execute arbitrary code with elevated privileges.

2. Exploitation Mechanics & Attack Scenario

To exploit this vulnerability, an attacker must first establish a valid local CLI session via SSH, Telnet, or the physical console port. Once authenticated with low-privilege access, the attacker inputs crafted, invalid CLI commands. The parser's failure to validate these inputs triggers a buffer overflow or memory corruption. The 'EPICBANANA' exploit tool, leaked by the Shadow Brokers, automates this process to inject a payload directly into memory, bypassing authentication checks and spawning a root-level shell.

3. Infrastructure & Business Impact

Cisco ASA appliances serve as critical perimeter security gateways and VPN concentrators for enterprise networks. A successful compromise of this device allows an attacker to disable firewall rules, intercept sensitive VPN traffic, and establish a persistent foothold. This effectively neutralizes the organization's perimeter defense, enabling unrestricted lateral movement across the internal network.