CVE-2015-0603 in Unified IP Phone 9900
Summary
by MITRE
Cisco Unified IP 9900 phones with firmware 9.4(.1) and earlier use weak permissions for unspecified files, which allows local users to cause a denial of service (persistent hang or reboot) by writing to a phone s filesystem, aka Bug ID CSCup90474.
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Analysis
by VulDB Data Team • 06/21/2017
The vulnerability identified as CVE-2015-0603 affects Cisco Unified IP 9900 phones running firmware versions 9.4.1 and earlier, representing a critical security flaw that undermines the device's integrity and availability. This issue stems from weak file permissions that permit local users to manipulate the phone's filesystem, creating a persistent threat vector that can be exploited to trigger system instability. The vulnerability operates within the context of a voice communication device that serves as a critical endpoint in enterprise telephony infrastructure, making it particularly concerning for organizations relying on unified communications systems. The bug ID CSCup90474 specifically documents this weakness in the phone's file system access controls, highlighting the insufficient privilege management that enables unauthorized modifications to system-critical components.
The technical implementation of this vulnerability exploits the phone's insufficient access control mechanisms, allowing local attackers with minimal privileges to write to critical system files within the device's filesystem. This flaw essentially provides a path for privilege escalation through file system manipulation, where an attacker can corrupt or overwrite essential configuration or executable files. The weak permissions likely extend to system directories or configuration files that should normally be protected from modification by non-privileged users. When malicious data is written to these locations, the phone's operating system becomes unstable and may either hang persistently or undergo an unexpected reboot, effectively rendering the communication device unusable. The vulnerability's persistence stems from the fact that the weak permissions remain unchanged across phone reboots, making the system vulnerable to repeated exploitation without requiring additional authentication or elevated privileges.
The operational impact of this vulnerability extends beyond simple denial of service, as it can severely disrupt enterprise communication networks where these phones serve as essential endpoints for voice and video conferencing. Organizations may experience cascading failures when multiple phones in a network become compromised, potentially affecting business continuity and emergency communication capabilities. The vulnerability's local nature means that attackers need physical access to the device or must already have user-level credentials, but the consequences remain severe since the attack can be executed repeatedly without additional authentication requirements. This weakness creates a persistent threat that can be exploited by insiders or attackers who gain access to the device's local network, potentially leading to extended service outages that require manual intervention to restore functionality. The impact is particularly significant in mission-critical environments such as healthcare facilities, emergency services, or financial institutions where communication reliability is paramount.
Mitigation strategies for CVE-2015-0603 should prioritize immediate firmware updates to versions that address the weak file permissions issue, as recommended by Cisco's security advisories. Organizations must conduct comprehensive inventory assessments to identify all affected devices and implement systematic update deployment processes to ensure complete coverage across their telephony infrastructure. Network segmentation and access control measures should be strengthened to limit local access to these devices, while monitoring systems should be configured to detect unusual file system modifications or reboot patterns that might indicate exploitation attempts. Security teams should also implement regular vulnerability scanning procedures to identify similar permission weaknesses in other networked devices and establish incident response protocols specifically addressing device-level denial of service attacks. The remediation process should include verification procedures to confirm that file system permissions have been properly hardened and that the device maintains expected operational behavior following the update process, ensuring that the vulnerability has been completely eliminated from the network infrastructure.