CVE-2018-15381 in Unity Express
Summary
by MITRE
A Java deserialization vulnerability in Cisco Unity Express (CUE) could allow an unauthenticated, remote attacker to execute arbitrary shell commands with the privileges of the root user. The vulnerability is due to insecure deserialization of user-supplied content by the affected software. An attacker could exploit this vulnerability by sending a malicious serialized Java object to the listening Java Remote Method Invocation (RMI) service. A successful exploit could allow the attacker to execute arbitrary commands on the device with root privileges.
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Analysis
by VulDB Data Team • 06/05/2023
This vulnerability represents a critical Java deserialization flaw in Cisco Unity Express systems that fundamentally undermines the security model of the affected platform. The vulnerability stems from the insecure handling of serialized Java objects within the RMI service, creating a pathway for remote code execution that bypasses traditional authentication mechanisms. The flaw exists in the way the system processes incoming serialized data without proper validation or sanitization, allowing attackers to craft malicious objects that when deserialized trigger unintended code execution. This type of vulnerability is particularly dangerous because it enables unauthenticated remote exploitation, meaning attackers can compromise systems without requiring valid credentials or prior access to the network.
The technical implementation of this vulnerability leverages the inherent risks associated with Java's deserialization mechanism, which is a known weakness that has been exploited in numerous high-profile attacks over the years. When the RMI service receives a malicious serialized object, the Java runtime deserializes the object and executes the embedded malicious code as part of the normal deserialization process. This process occurs within the context of the running service, which in this case operates with root privileges, thereby granting attackers complete system control. The vulnerability specifically targets the deserialization logic within the Unity Express platform's Java components, where the system fails to validate the source or integrity of the serialized data before processing it.
The operational impact of this vulnerability extends far beyond simple remote code execution, as it provides attackers with root-level access to the entire system. This privilege escalation allows malicious actors to perform actions such as modifying system files, installing backdoors, accessing sensitive data, and potentially using the compromised system as a pivot point for further attacks within the network. The vulnerability's remote nature means that attackers can exploit it from anywhere on the internet without requiring physical access or network proximity to the target system. This characteristic makes the vulnerability particularly attractive to threat actors who seek to compromise systems at scale, as demonstrated by various attack campaigns that have targeted similar deserialization vulnerabilities in enterprise applications.
Mitigation strategies for this vulnerability should focus on immediate patching and architectural defenses to prevent similar issues in the future. Cisco has released security updates that address the deserialization vulnerability by implementing proper input validation and sanitization measures within the affected RMI service. Organizations should prioritize applying these patches immediately while also implementing network segmentation to limit exposure of vulnerable services to untrusted networks. Additional defensive measures include disabling unnecessary RMI services, implementing network access controls, and monitoring for suspicious deserialization activity. From a compliance perspective, this vulnerability aligns with CWE-502 which specifically addresses deserialization of untrusted data, and it maps to attack techniques in the MITRE ATT&CK framework under T1059 for command and scripting interpreter, as well as T1068 for exploit for privilege escalation. The vulnerability demonstrates the critical importance of validating all input data and implementing proper security controls around serialization mechanisms in enterprise applications, particularly those handling remote connections and privileged operations.