CVE-2015-0692 in Web Security Appliance
Summary
by MITRE
Cisco Web Security Appliance (WSA) devices with software 8.5.0-ise-147 do not properly restrict use of the pickle Python module during certain tunnel-status checks, which allows local users to execute arbitrary Python code and gain privileges via crafted serialized objects, aka Bug ID CSCut39230.
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Analysis
by VulDB Data Team • 05/03/2022
The vulnerability identified as CVE-2015-0692 affects Cisco Web Security Appliance devices running software version 8.5.0-ise-147 and represents a critical privilege escalation flaw that stems from improper handling of Python pickle module operations. This vulnerability specifically manifests during tunnel-status checks where the system fails to adequately validate serialized data, creating an attack surface that allows local users to execute arbitrary code with elevated privileges. The pickle module in Python is designed for serializing and deserializing Python object structures, but when improperly used, it can become a vector for code execution attacks due to its ability to execute arbitrary code during the deserialization process.
The technical flaw resides in the WSA's handling of serialized data within the tunnel-status checking functionality, where the system employs the pickle module without proper input validation or sanitization measures. This creates a classic deserialization vulnerability that falls under the category of CWE-502, which specifically addresses "Deserialization of Untrusted Data" in software systems. When a local user crafts malicious serialized objects and feeds them to the vulnerable system, the pickle module deserializes these objects and executes the embedded code, bypassing normal security restrictions and privilege boundaries. The attack requires local system access but can result in complete system compromise, allowing attackers to escalate privileges and gain administrative control over the appliance.
The operational impact of this vulnerability extends beyond simple code execution, as it fundamentally undermines the security model of the Cisco Web Security Appliance by enabling local privilege escalation attacks. An attacker with local access can leverage this vulnerability to gain root privileges on the device, potentially compromising the entire network security infrastructure that the appliance is designed to protect. This vulnerability affects organizations that rely on Cisco WSA for web filtering and security enforcement, as the compromise of such a device can lead to complete network infiltration, data exfiltration, and disruption of security controls. The attack vector is particularly concerning because it requires minimal privileges to exploit and can be executed by any user with local access to the system, making it a significant risk for environments where local access is not strictly controlled.
Organizations should implement immediate mitigations including applying the relevant Cisco security patches and updates that address this vulnerability, as well as implementing network segmentation to limit local access to critical security appliances. System administrators should also consider disabling unnecessary Python modules and implementing strict input validation controls to prevent similar issues in other applications. The vulnerability aligns with ATT&CK technique T1059.006, which covers "Python" as a command and scripting language, and T1068, which addresses "Exploitation for Privilege Escalation" in cybersecurity frameworks. Additionally, this issue demonstrates the importance of following secure coding practices and the principle of least privilege when implementing serialization mechanisms in security-critical applications, as outlined in various cybersecurity standards and best practices.