CVE-2016-1435 in 8800 IP Phone
Summary
by MITRE
Cisco 8800 phones with software 11.0(1) do not properly enforce mounted-filesystem permissions, which allows local users to write to arbitrary files by leveraging shell access, aka Bug ID CSCuz03014.
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Analysis
by VulDB Data Team • 02/05/2019
The vulnerability identified as CVE-2016-1435 affects Cisco 8800 series IP phones running software version 11.0(1) and represents a critical local privilege escalation flaw within the device's filesystem permissions model. This issue stems from inadequate enforcement of mounted filesystem permissions, creating a significant security gap that allows authenticated local users to bypass normal access controls and write to arbitrary files on the device. The vulnerability is particularly concerning because it leverages existing shell access capabilities to escalate privileges and gain unauthorized write access to critical system files, potentially enabling full device compromise.
The technical flaw manifests through improper permission handling on mounted filesystems within the Cisco 8800 phone's operating environment. When local users possess shell access, they can exploit this weakness to manipulate filesystem permissions and gain write access to files that should normally be restricted. This behavior violates fundamental security principles of least privilege and proper access control enforcement, as outlined in the CWE-276 (Improper Ownership) and CWE-273 (Improper Check for Unusual or Exceptional Conditions) categories. The vulnerability essentially allows an attacker with minimal privileges to escalate their access level and modify critical system components, potentially leading to persistent backdoor access or complete system compromise.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with the capability to modify core system files and potentially install malicious code. An attacker who gains local shell access can leverage this flaw to modify configuration files, system binaries, or other critical components that control the phone's operation and security settings. This could result in unauthorized call routing, data exfiltration, or complete device takeover. The vulnerability affects enterprise voice systems where these phones are deployed, potentially compromising the entire communication infrastructure and violating security compliance requirements. According to ATT&CK framework category T1068 (Local Privilege Escalation), this vulnerability represents a direct pathway for attackers to elevate their privileges within the targeted system.
Mitigation strategies for CVE-2016-1435 should focus on immediate software updates and access control hardening. Cisco has released patches addressing this specific vulnerability in subsequent software releases, making it essential for organizations to apply the appropriate firmware updates to affected devices. Network administrators should also implement strict access controls and monitor for unauthorized shell access attempts, as the vulnerability requires local access to exploit. Additionally, organizations should consider implementing network segmentation to limit physical or remote access to these devices, reducing the attack surface and preventing unauthorized users from gaining the initial shell access required to exploit this flaw. The remediation process should include comprehensive testing of updated firmware to ensure that the patch does not introduce compatibility issues with existing telephony services and that all security configurations remain intact.