CVE-2015-6343 in IOS
Summary
by MITRE
The SIP implementation in Cisco IOS 15.5(3)M on Cisco Unified Border Element (CUBE) devices allows remote attackers to cause a denial of service via crafted SIP messages, aka Bug ID CSCuv79202.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/01/2018
The vulnerability identified as CVE-2015-6343 affects Cisco IOS version 15.5(3)M running on Cisco Unified Border Element devices, specifically targeting the Session Initiation Protocol implementation. This flaw represents a critical denial of service vulnerability that can be exploited by remote attackers without authentication, making it particularly dangerous in production environments where SIP communication is essential for voice and video services. The vulnerability stems from insufficient input validation within the SIP message processing mechanisms of the CUBE implementation, creating an opportunity for malicious actors to disrupt critical communication infrastructure.
The technical nature of this vulnerability involves a buffer overflow or memory corruption issue that occurs when the Cisco IOS SIP stack processes malformed or specially crafted SIP messages. When legitimate SIP traffic is received with specific malformed parameters or sequences, the system fails to properly validate the message structure, leading to unexpected behavior that can result in device crashes or complete system restarts. This type of vulnerability typically falls under CWE-121, which describes buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw specifically impacts the SIP parser component within the CUBE functionality, which is responsible for handling signaling messages between different SIP entities in unified communications environments.
The operational impact of this vulnerability extends beyond simple service disruption, as it can compromise the entire communication infrastructure managed by the affected CUBE device. Organizations relying on Cisco Unified Border Elements for voice traffic routing and security enforcement face significant risks including complete loss of voice services, potential network partitioning, and extended downtime during recovery operations. Attackers can exploit this vulnerability to repeatedly cause service interruptions, making it particularly damaging for mission-critical environments where communication availability is paramount. The vulnerability also represents a potential stepping stone for more sophisticated attacks, as initial denial of service can be used to create opportunities for further exploitation or to mask other malicious activities within the network.
Mitigation strategies for CVE-2015-6343 should prioritize immediate patching of affected Cisco IOS versions, with organizations implementing the latest security updates from Cisco that address the SIP message processing flaws. Network administrators should also consider implementing SIP-specific filtering rules and rate limiting mechanisms to reduce the impact of malformed messages, while monitoring for unusual traffic patterns that may indicate exploitation attempts. The vulnerability aligns with several ATT&CK techniques including T1498 for network denial of service and T1071 for application layer protocols, emphasizing the need for comprehensive network security monitoring. Additionally, organizations should conduct regular vulnerability assessments and maintain updated network segmentation strategies to limit the potential blast radius of such exploits, ensuring that even if one device is compromised, the broader communication infrastructure remains protected.