CVE-2013-1194 in ASA 5500
Summary
by MITRE
The ISAKMP implementation on Cisco Adaptive Security Appliances (ASA) devices generates different responses for IKE aggressive-mode messages depending on whether invalid VPN groups are specified, which allows remote attackers to enumerate groups via a series of messages, aka Bug ID CSCue73708.
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Analysis
by VulDB Data Team • 04/30/2017
The vulnerability identified as CVE-2013-1194 resides within the ISAKMP implementation of Cisco Adaptive Security Appliances, specifically affecting the IKE aggressive-mode message processing functionality. This weakness manifests when the ASA device encounters invalid VPN groups during the initial IKE negotiation phase, creating a distinguishable behavioral difference in the system's response patterns that can be exploited by remote attackers to perform group enumeration attacks. The vulnerability represents a significant security flaw in the authentication and authorization mechanisms of the ASA platform, as it inadvertently reveals information about the system's internal group configurations through subtle response variations.
The technical implementation flaw stems from the inconsistent handling of invalid VPN group references within the IKE aggressive-mode exchange process. When a remote attacker submits IKE messages containing references to non-existent VPN groups, the ASA responds differently compared to when valid groups are specified, creating a timing or response pattern differential that can be systematically analyzed. This behavior violates fundamental security principles of consistent error handling and information hiding, as the device's response should remain uniform regardless of the input provided. The vulnerability specifically impacts the ISAKMP (Internet Security Association and Key Management Protocol) implementation within the ASA's IKE daemon, where the aggressive mode exchange is processed without maintaining consistent response characteristics for invalid inputs.
From an operational impact perspective, this vulnerability enables remote attackers to perform reconnaissance activities that can significantly compromise the security posture of the affected network infrastructure. The enumeration capability allows adversaries to discover valid VPN group configurations, which can then be leveraged to craft more sophisticated attacks targeting specific authentication mechanisms or to identify potential attack vectors within the network's security architecture. This information disclosure vulnerability can facilitate subsequent attacks such as credential stuffing, privilege escalation attempts, or targeted exploitation of other system components that rely on the discovered group configurations. The impact extends beyond simple information gathering as it provides attackers with insights into the internal security architecture that could be used to bypass other protective measures.
The vulnerability aligns with CWE-200 (Information Exposure) and CWE-310 (Cryptographic Issues) categories, as it exposes internal system information through inconsistent response patterns and potentially weak cryptographic implementations. From an ATT&CK framework perspective, this vulnerability maps to T1087.001 (Account Discovery - Local Account) and T1590.001 (Reconnaissance - Network Scanning), as it enables attackers to discover and enumerate valid authentication groups within the system. The consistent response differential provides attackers with a reliable method for information gathering that can be automated and scaled, making it particularly dangerous in environments where multiple ASA devices are deployed and where the enumeration process can be repeated across different time windows to validate findings. Organizations should implement immediate mitigations including applying Cisco's security patches, configuring access controls to limit IKE traffic, and monitoring for anomalous IKE message patterns that could indicate enumeration attempts.
The underlying security implications extend to the broader principles of defense in depth, as this vulnerability demonstrates how seemingly minor implementation flaws in core security protocols can create significant reconnaissance opportunities for attackers. The vulnerability highlights the importance of consistent error handling in security-critical systems and the need for rigorous testing of edge cases in authentication protocols. Organizations should also consider implementing network segmentation to limit the exposure of ASA devices to untrusted networks and establish monitoring procedures that can detect and alert on unusual IKE message patterns that might indicate exploitation attempts. The vulnerability serves as a reminder that even well-established security protocols can contain implementation weaknesses that require careful attention and regular security assessments to maintain effective protection against evolving threats.