CVE-2013-6685 in Unified IP Phone 9900
Summary
by MITRE
The firmware on Cisco Unified IP phones 8961, 9951, and 9971 uses weak permissions for memory block devices, which allows local users to gain privileges by mounting a device with a setuid file in its filesystem, aka Bug ID CSCui04382.
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Analysis
by VulDB Data Team • 05/15/2018
The vulnerability identified as CVE-2013-6685 affects Cisco Unified IP phones model numbers 8961, 9951, and 9971, representing a critical privilege escalation flaw within the device firmware. This issue stems from inadequate permission controls applied to memory block devices within the phone's operating system, creating exploitable conditions that allow local attackers to elevate their system privileges. The vulnerability specifically manifests when a malicious user mounts a device containing a setuid file within the phone's filesystem, enabling unauthorized privilege escalation.
The technical root cause of this vulnerability aligns with CWE-276, which addresses improper permissions for system resources, and more specifically relates to CWE-732, which covers inadequate protection of system resources. The flaw exists in the firmware implementation where memory block devices are not properly secured, allowing local users to manipulate filesystem permissions and execute setuid binaries with elevated privileges. This represents a fundamental breakdown in the principle of least privilege that should be enforced within embedded operating systems.
The operational impact of this vulnerability is significant as it provides local attackers with the capability to gain administrative privileges on affected Cisco IP phones. This privilege escalation allows attackers to potentially access sensitive phone configuration data, modify phone settings, intercept communications, or even install malicious software on the device. The vulnerability is particularly concerning because it requires only local access to the device, meaning an attacker who has physical access or can establish a local network presence could exploit this flaw without requiring external network connectivity or complex attack vectors.
From an attack perspective, this vulnerability maps to several ATT&CK techniques including privilege escalation through exploitation of weak permissions and potentially to persistence mechanisms if the attacker can maintain access after gaining elevated privileges. The attack surface is limited to local access scenarios but represents a serious security risk for enterprise voice environments where IP phones serve as critical communication infrastructure. Organizations using these specific Cisco phone models face potential exposure to internal threats or physical security breaches that could lead to complete device compromise and subsequent network infiltration.
Mitigation strategies for this vulnerability should include immediate firmware updates from Cisco addressing the permission flaws in memory block device handling. Network administrators should also implement strict physical security controls for IP phone devices, particularly in sensitive environments where unauthorized access could be exploited. Additional protective measures include monitoring for unauthorized device mounting activities and ensuring that only trusted users have local access to these devices. The vulnerability highlights the importance of proper permission management in embedded systems and underscores the need for regular security assessments of firmware components in network infrastructure devices.