CVE-2012-3924 in IOS
Summary
by MITRE
The SSLVPN implementation in Cisco IOS 15.1 and 15.2, when DTLS is enabled, does not properly handle certain outbound ACL configurations, which allows remote authenticated users to cause a denial of service (device crash) via a session involving a PPP over ATM (PPPoA) interface, aka Bug ID CSCty97961.
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Analysis
by VulDB Data Team • 04/17/2017
The vulnerability identified as CVE-2012-3924 represents a critical flaw in Cisco IOS software versions 15.1 and 15.2 that affects SSLVPN implementations when DTLS protocol is enabled. This weakness specifically manifests in the handling of outbound access control list configurations within the network infrastructure, creating a pathway for malicious actors to exploit the system through carefully crafted network sessions. The vulnerability is particularly concerning as it affects the core routing and switching functionality of Cisco devices, potentially compromising network availability and operational continuity for organizations relying on these platforms for secure remote access.
The technical implementation flaw occurs within the SSLVPN subsystem of Cisco IOS when it processes network sessions involving PPPoA interfaces while DTLS is active. The system fails to properly validate or process certain outbound ACL configurations, creating a condition where authenticated remote users can manipulate session establishment parameters to trigger a device crash. This issue stems from inadequate input validation and error handling within the SSLVPN processing pipeline, where the system does not adequately sanitize the interaction between the DTLS protocol implementation and the access control list processing mechanisms. The vulnerability is classified under CWE-248, which addresses "Uncaught Exception" conditions in software implementations, specifically when network protocol handling fails to properly account for edge cases in session management.
The operational impact of this vulnerability extends beyond simple service disruption, as it can lead to complete device unavailability and potential network segmentation issues for organizations utilizing Cisco IOS for remote access solutions. When exploited, the vulnerability allows authenticated attackers to cause denial of service conditions that result in device crashes, requiring manual intervention for system recovery and potentially leading to extended downtime for critical network services. Network administrators may experience significant operational challenges as the vulnerability can be triggered through legitimate user sessions, making detection and prevention difficult. The attack vector specifically targets SSLVPN sessions over PPPoA interfaces, which are commonly used in enterprise environments for providing secure remote access to network resources, thereby amplifying the potential impact on business operations.
Mitigation strategies for CVE-2012-3924 should prioritize immediate patch management through Cisco's official security advisories, as the vulnerability requires software updates to address the underlying code flaws in the SSLVPN implementation. Organizations should implement network segmentation to isolate affected devices and limit the potential attack surface, while also monitoring for suspicious authentication patterns that might indicate exploitation attempts. Security teams should consider temporarily disabling DTLS functionality when it is not essential for operations, and implementing additional logging and monitoring for SSLVPN session establishment to detect anomalous behavior. The vulnerability's classification under ATT&CK technique T1499.004 for "Network Denial of Service" highlights the importance of implementing robust network resilience measures and maintaining up-to-date threat intelligence to prevent exploitation attempts. Organizations should also conduct thorough security assessments of their SSLVPN configurations to identify and remediate similar vulnerabilities in their network infrastructure.