CVE-2016-6392 in IOS
Summary
by MITRE
Cisco IOS 12.2 and 15.0 through 15.3 and IOS XE 3.1 through 3.9 allow remote attackers to cause a denial of service (device restart) via a crafted IPv4 Multicast Source Discovery Protocol (MSDP) Source-Active (SA) message, aka Bug ID CSCud36767.
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Analysis
by VulDB Data Team • 04/29/2019
The vulnerability identified as CVE-2016-6392 represents a critical denial of service flaw affecting Cisco IOS versions 12.2 and 15.0 through 15.3, along with IOS XE versions 3.1 through 3.9. This issue specifically targets the Multicast Source Discovery Protocol implementation within Cisco networking equipment, creating a scenario where remote attackers can deliberately induce device restarts through the manipulation of crafted IPv4 MSDP Source-Active messages. The flaw resides in the improper handling of malformed MSDP SA messages, which are essential components of the multicast routing protocol used to distribute multicast source information across networks. When these malformed packets are received by affected Cisco devices, they trigger an unexpected system behavior that ultimately results in complete device restarts, effectively disrupting network operations and availability.
The technical exploitation of this vulnerability occurs through the manipulation of MSDP SA messages, which are used to advertise multicast source information between MSDP peers in multicast networks. The flaw manifests when the Cisco IOS software fails to properly validate or process the fields within these Source-Active messages, particularly in how it handles certain combinations of multicast group addresses, source addresses, and associated flags. This improper input validation creates a condition where the device's memory management or processing routines encounter malformed data that causes the system to crash or restart. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, specifically in the context of network protocol processing where the software does not adequately validate the boundaries and structures of incoming multicast messages. The operational impact extends beyond simple service disruption as the repeated exploitation can lead to sustained network outages, particularly in environments where multicast routing is heavily utilized for video streaming, online gaming, or other multicast-based applications.
The security implications of CVE-2016-6392 align with ATT&CK technique T1499.004, which describes the use of network denial of service attacks to disrupt services through device restarts. Network administrators face significant challenges when addressing this vulnerability since the attack can be executed remotely without requiring authentication or specialized access privileges, making it particularly dangerous in production environments. The attack vector leverages the inherent multicast routing protocols that many organizations rely upon for efficient data distribution, meaning that even a single compromised device can potentially affect larger network segments. Organizations utilizing Cisco devices in multicast environments must recognize that this vulnerability can be exploited by adversaries with minimal technical expertise, as it requires only the ability to send crafted packets to the affected device. The vulnerability's impact is exacerbated in large enterprise networks where multicast routing is extensively deployed, as the restart of multiple devices can cascade through the network infrastructure and create widespread service disruption. The flaw demonstrates the critical importance of proper input validation in network protocol implementations and highlights the need for robust error handling mechanisms in routing software to prevent malformed data from causing system instability.
Mitigation strategies for CVE-2016-6392 should include immediate deployment of Cisco's security patches and software updates that address the MSDP message processing flaw. Network administrators should implement access control measures to restrict MSDP peer relationships to trusted sources only, effectively limiting the attack surface by preventing unauthorized entities from sending malicious MSDP messages. The implementation of network segmentation and filtering rules at the multicast routing boundaries can help contain the impact of potential exploitation attempts. Additionally, monitoring systems should be configured to detect unusual restart patterns or MSDP message traffic anomalies that could indicate exploitation attempts. Organizations should also consider implementing network intrusion detection systems that can identify and alert on malformed MSDP packets, providing early warning capabilities for potential attacks. The vulnerability serves as a reminder of the critical need for regular security assessments and patch management programs, particularly for core networking infrastructure components that handle protocol processing. Network teams should also conduct regular testing of their systems' resilience to similar protocol-based attacks and maintain detailed incident response procedures that account for potential multicast routing disruptions. The remediation process requires careful planning to avoid unintended network disruptions during patch deployment, as the affected devices may need to be restarted to apply the security fixes properly.