CVE-2013-6682 in ASA
Summary
by MITRE
The phone-proxy implementation in Cisco Adaptive Security Appliance (ASA) Software 9.0.3.6 and earlier does not properly validate X.509 certificates, which allows remote attackers to cause a denial of service (connection-database corruption) via an invalid entry, aka Bug ID CSCui33299.
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Analysis
by VulDB Data Team • 05/15/2017
The vulnerability described in CVE-2013-6682 represents a critical flaw in Cisco Adaptive Security Appliance software that specifically affects versions 9.0.3.6 and earlier. This issue resides within the phone-proxy implementation component of the ASA software, which is designed to handle telephone-related traffic and communications. The vulnerability stems from inadequate validation of X.509 certificates, which are fundamental cryptographic certificates used to establish trust and authenticate entities in secure communications. When the system encounters improperly formatted or invalid X.509 certificate entries, it fails to properly validate these inputs before processing them, creating a pathway for malicious actors to exploit the system's certificate handling mechanisms.
The technical flaw manifests when remote attackers submit malformed X.509 certificate data through the phone-proxy functionality, causing the system to process these invalid entries without proper sanitization. This improper validation leads to connection database corruption, which fundamentally compromises the integrity of the ASA's connection tracking mechanisms. The vulnerability operates at the certificate validation layer where the system should enforce strict parsing and validation rules but instead allows malformed certificate data to propagate through the system. This flaw directly relates to CWE-248, which addresses the issue of an exception being thrown for an unknown error condition, and also connects to CWE-254, addressing weaknesses in cryptographic implementations that allow for improper certificate handling.
The operational impact of this vulnerability is severe, as it enables remote attackers to execute a denial of service attack against the affected ASA appliances. When the connection database becomes corrupted, legitimate users may experience complete loss of connectivity and communication services through the appliance. The corruption affects the system's ability to maintain accurate connection state information, potentially causing the appliance to crash or become unresponsive. This type of attack can be particularly damaging in enterprise environments where ASA appliances serve as critical network security gateways, potentially disrupting business operations and communication infrastructure. The vulnerability aligns with ATT&CK technique T1499.004, which involves network disruption through the corruption of network infrastructure components, and also maps to T1071.004, which covers application layer protocol usage for command and control communications.
Mitigation strategies for this vulnerability should begin with immediate implementation of Cisco's recommended security patches and updates to versions that address the certificate validation flaw. Organizations should also implement network segmentation and access controls to limit exposure of vulnerable ASA appliances to untrusted networks. Monitoring systems should be enhanced to detect anomalous certificate validation patterns and potential exploitation attempts. Additionally, administrators should consider implementing certificate management policies that enforce strict validation requirements and regularly audit certificate usage within the network infrastructure. The fix typically involves strengthening the X.509 certificate parsing logic to properly validate all incoming certificate data before processing, preventing malformed entries from corrupting the connection database. This vulnerability demonstrates the critical importance of proper cryptographic implementation and validation in network security appliances, where weaknesses in certificate handling can lead to complete service disruption and compromise of enterprise network security posture.