CVE-2016-9553 in Web Appliance
Summary
by MITRE
The Sophos Web Appliance (version 4.2.1.3) is vulnerable to two Remote Command Injection vulnerabilities affecting its web administrative interface. These vulnerabilities occur in the MgrReport.php (/controllers/MgrReport.php) component responsible for blocking and unblocking IP addresses from accessing the device. The device doesn't properly escape the information passed in the variables 'unblockip' and 'blockip' before calling the shell_exec() function which allows for system commands to be injected into the device. The code erroneously suggests that the information handled is protected by utilizing the variable name 'escapedips' - however this was not the case. The Sophos ID is NSWA-1258.
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Analysis
by VulDB Data Team • 05/16/2026
The vulnerability identified as CVE-2016-9553 represents a critical remote command injection flaw within the Sophos Web Appliance version 4.2.1.3, specifically targeting its web administrative interface. This security weakness resides in the MgrReport.php component which manages IP address blocking and unblocking operations, making it a prime target for attackers seeking unauthorized system access. The vulnerability stems from improper input validation and sanitization mechanisms that fail to adequately escape user-supplied data before processing, creating a direct pathway for malicious command execution within the appliance's underlying operating system. The affected device processes information through the 'unblockip' and 'blockip' variables without proper sanitization, allowing attackers to inject arbitrary shell commands that are subsequently executed with the privileges of the web application service account.
The technical implementation of this vulnerability demonstrates a classic command injection flaw that aligns with CWE-77, which categorizes improper neutralization of special elements used in OS commands. The code's erroneous assumption that the 'escapedips' variable provides adequate protection reveals a fundamental security misconfiguration where developers incorrectly believed that variable naming conventions would suffice for input sanitization. This misconception represents a critical oversight in secure coding practices, as the actual implementation fails to employ proper escaping mechanisms or input validation before invoking the shell_exec() function. The vulnerability operates at the application layer and requires no authentication for exploitation, making it particularly dangerous as it can be triggered through the web interface without prior access credentials. Attackers can leverage this weakness to execute arbitrary system commands, potentially leading to complete system compromise and unauthorized access to sensitive network resources.
The operational impact of this vulnerability extends beyond simple command execution, as it provides attackers with the capability to manipulate network traffic controls, access system logs, and potentially escalate privileges within the appliance environment. The affected MgrReport.php component controls critical network access policies, meaning successful exploitation could allow attackers to bypass security controls, block legitimate users, or create persistent backdoors within the network infrastructure. This vulnerability directly impacts the appliance's ability to maintain network security and integrity, potentially enabling attackers to use the device as a pivot point for further attacks within the network. The attack surface is particularly concerning given that the vulnerability affects the administrative interface, which typically requires elevated privileges and is designed to be protected from unauthorized access.
Mitigation strategies for CVE-2016-9553 should prioritize immediate implementation of the vendor's security patch, as the vulnerability has been addressed in subsequent versions of the Sophos Web Appliance software. Organizations should implement network segmentation to limit access to the administrative interface, restrict access to specific IP addresses, and deploy intrusion detection systems to monitor for suspicious command execution patterns. The remediation process should include thorough input validation and sanitization of all user-supplied data, proper implementation of parameterized queries, and comprehensive security testing of all web application components. Additionally, organizations should conduct regular security assessments of their network infrastructure to identify similar vulnerabilities in other devices and applications, ensuring that the security practices align with industry standards such as those outlined in the OWASP Top Ten and NIST cybersecurity frameworks. The vulnerability also highlights the importance of proper code review processes and security training for developers to prevent similar issues in future implementations.