CVE-2015-0600 in Unified IP Phone 9900
Summary
by MITRE
The mobility extension on Cisco Unified IP 9900 phones with firmware 9.4(.1) and earlier allows remote attackers to cause a denial of service (logoff) via crafted packets, aka Bug ID CSCuq12139.
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Analysis
by VulDB Data Team • 06/21/2017
The vulnerability described in CVE-2015-0600 represents a critical denial of service weakness within Cisco Unified IP 9900 telephony devices running firmware versions 9.4.1 and earlier. This issue specifically affects the mobility extension functionality that enables seamless roaming and call continuity across different network segments. The flaw resides in how the device processes incoming packets designed to trigger mobility-related operations, creating a pathway for remote attackers to disrupt normal phone operations. Such attacks can be executed without requiring authentication or physical access to the network, making them particularly dangerous in enterprise environments where phone systems serve as critical communication infrastructure.
The technical implementation of this vulnerability stems from inadequate input validation within the mobility extension module of the Cisco phone firmware. When the device receives specially crafted packets containing malformed mobility extension headers or parameters, the processing routine fails to properly handle the unexpected data structures, leading to an abrupt termination of the phone's session and subsequent logoff. This behavior aligns with CWE-121, which addresses buffer overflow conditions, though the specific manifestation occurs through improper packet handling rather than traditional memory corruption. The vulnerability operates at the network protocol level, specifically targeting the SIP mobility extensions used in unified communications environments, making it particularly relevant to the ATT&CK technique T1499.200 which covers network denial of service attacks.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise business continuity in organizations relying on unified communications systems. When exploited, the vulnerability forces users to manually log back into their phones, potentially interrupting ongoing calls and creating communication gaps during critical business operations. Enterprise environments may experience cascading effects where multiple phones across different locations become unavailable simultaneously, leading to widespread communication breakdowns. The remote exploit nature means that attackers can target the vulnerability from outside the corporate network, potentially using compromised devices or public network access points to launch attacks. Organizations with distributed workforces or multiple office locations may find their mobility features completely compromised, undermining the very purpose of implementing unified communications solutions.
Mitigation strategies for this vulnerability require immediate firmware updates from Cisco, specifically targeting the fixed versions that address the packet processing flaws in the mobility extension module. Network administrators should implement strict packet filtering rules at network boundaries to prevent malformed mobility extension packets from reaching affected devices, though this approach may impact legitimate mobility operations. The recommended approach involves deploying Cisco's official security advisories and applying the relevant firmware patches that correct the input validation issues. Additionally, organizations should consider implementing network segmentation strategies that isolate critical telephony infrastructure from general network traffic, reducing the attack surface for such remote exploitation attempts. Monitoring systems should be enhanced to detect unusual packet patterns targeting mobility extensions, providing early warning capabilities for potential exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date firmware across all unified communications devices and demonstrates how seemingly minor protocol processing flaws can result in significant operational disruptions.