CVE-2018-16604 in Nibbleblog
Summary
by MITRE
An issue was discovered in Nibbleblog v4.0.5. With an admin's username and password, an attacker can execute arbitrary PHP code by changing the username because the username is surrounded by double quotes (e.g., "${phpinfo()}").
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Analysis
by VulDB Data Team • 05/07/2023
This vulnerability exists in Nibbleblog version 4.0.5 and represents a critical code injection flaw that allows authenticated attackers to execute arbitrary PHP code. The issue stems from improper input validation and sanitization within the application's user management functionality where the username parameter is directly embedded into PHP code without adequate escaping or sanitization. When an attacker with administrative credentials modifies a username field, the system fails to properly escape special characters, creating a path for code injection attacks. The vulnerability specifically manifests when the username contains PHP code enclosed in double quotes, as demonstrated by the example "${phpinfo()}" which would be executed as PHP code rather than treated as literal text. This represents a classic case of improper input handling that violates security best practices and creates a severe privilege escalation vector.
The technical implementation of this vulnerability follows a pattern consistent with command injection and code injection attack vectors as classified under CWE-94, which deals with "Improper Control of Generation of Code ('Code Injection')". The flaw occurs because the application does not properly sanitize user-supplied input before incorporating it into dynamically generated PHP code. This allows attackers to inject malicious PHP code that gets executed within the application context, potentially providing full system compromise capabilities. The vulnerability is particularly dangerous because it requires only administrative authentication, meaning that an attacker who has gained access to administrative credentials can leverage this flaw to execute arbitrary code on the server. The use of double quotes in the injection payload demonstrates that the application's code generation process is not properly escaping or sanitizing user input, creating a direct pathway for PHP code execution.
From an operational perspective, this vulnerability creates significant risk for organizations using Nibbleblog 4.0.5 as it enables attackers with administrative access to escalate their privileges to full system compromise. The impact extends beyond simple code execution to potential data exfiltration, system reconnaissance, and further lateral movement within the network. Attackers can leverage this vulnerability to execute system commands, access sensitive data, modify content, or establish persistent backdoors. The attack surface is particularly concerning because it requires minimal additional privileges beyond administrative access, making it an attractive target for attackers who have already compromised administrative credentials. This vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1078.004 for "Valid Accounts: Cloud Accounts" when considering the broader attack chain that could follow such a code execution capability.
The recommended mitigation strategies include immediate patching of the Nibbleblog application to version 4.0.6 or later, which addresses this specific code injection vulnerability. Organizations should also implement input validation and sanitization measures to ensure that user-supplied data cannot be interpreted as executable code. Additionally, administrators should enforce the principle of least privilege and implement robust monitoring for unusual administrative activities. The vulnerability highlights the importance of proper code review practices and input sanitization, particularly for applications that dynamically generate code or configuration files. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other applications. Organizations should also consider implementing web application firewalls and runtime application self-protection mechanisms to detect and prevent similar injection attacks. The incident underscores the critical need for security awareness training and secure coding practices to prevent such vulnerabilities from being introduced in the first place.