CVE-2018-0253 in Secure Access Control System
Summary
by MITRE
A vulnerability in the ACS Report component of Cisco Secure Access Control System (ACS) could allow an unauthenticated, remote attacker to execute arbitrary commands on an affected system. Commands executed by the attacker are processed at the targeted user's privilege level. The vulnerability is due to insufficient validation of the Action Message Format (AMF) protocol. An attacker could exploit this vulnerability by sending a crafted AMF message that contains malicious code to a targeted user. A successful exploit could allow the attacker to execute arbitrary commands on the ACS device. This vulnerability affects all releases of Cisco Secure ACS prior to Release 5.8 Patch 7. Cisco Bug IDs: CSCve69037.
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Analysis
by VulDB Data Team • 03/08/2023
The vulnerability identified as CVE-2018-0253 resides within the ACS Report component of Cisco Secure Access Control System, representing a critical remote code execution flaw that undermines the security posture of affected deployments. This weakness specifically targets the Action Message Format (AMF) protocol implementation, which serves as a communication framework for data exchange within the system. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize or verify the integrity of AMF messages received by the ACS device. Attackers can exploit this by crafting malicious AMF payloads that contain executable code, bypassing authentication requirements entirely. The flaw affects all versions of Cisco Secure ACS prior to Release 5.8 Patch 7, indicating a prolonged window of exposure for organizations utilizing these systems. This vulnerability represents a significant concern given that it operates at the application layer and can be exploited without requiring any prior authentication credentials, making it particularly dangerous in networked environments where such systems are deployed.
The technical exploitation of CVE-2018-0253 leverages the insufficient validation of AMF protocol elements to inject malicious code that executes within the context of the targeted user's privileges. When an attacker sends a crafted AMF message containing malicious payload, the ACS system processes this input without adequate sanitization, allowing arbitrary command execution to occur. The execution occurs at the privilege level of the targeted user, meaning that if the system operates with elevated privileges, attackers could potentially gain administrative control over the entire ACS infrastructure. This vulnerability operates under the ATT&CK framework as a remote code execution technique, specifically categorized under T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter), demonstrating how attackers can leverage protocol implementation weaknesses to achieve unauthorized system access. The vulnerability aligns with CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-20 (Improper Input Validation), highlighting the fundamental security flaws in input sanitization and output handling mechanisms.
The operational impact of this vulnerability extends beyond simple command execution, as it fundamentally compromises the integrity and confidentiality of the entire access control infrastructure. Organizations relying on Cisco Secure ACS for network authentication and authorization face potential complete system compromise, allowing attackers to manipulate user access rights, extract sensitive authentication data, or establish persistent backdoors within their network environments. The vulnerability's ability to execute commands at the target user's privilege level means that exploitation could result in unauthorized access to network resources, modification of access control policies, or even complete takeover of the authentication system. This poses significant risks to enterprise security postures, particularly in environments where the ACS system serves as a central authentication authority for network access. The impact is further compounded by the fact that the vulnerability affects all pre-patch versions, meaning that organizations with legacy deployments may have been exposed for extended periods without detection.
Mitigation strategies for CVE-2018-0253 center on immediate patch deployment to Cisco Secure ACS Release 5.8 Patch 7, which contains the necessary fixes for the AMF validation issues. Organizations should prioritize updating their systems to the latest supported release, as this vulnerability affects multiple versions and requires specific patching to resolve. Network segmentation and access controls should be implemented to limit exposure of the ACS system to untrusted networks, reducing the attack surface available to potential attackers. Additional protective measures include monitoring network traffic for suspicious AMF protocol communications, implementing intrusion detection systems to identify malformed AMF messages, and conducting thorough security assessments of existing ACS deployments to identify any unauthorized modifications. Organizations should also consider implementing network access controls that restrict communication to the ACS system to only trusted sources and ports. The vulnerability's classification under both CWE and ATT&CK frameworks emphasizes the need for comprehensive security controls that address both input validation weaknesses and operational security monitoring to prevent exploitation.