CVE-2000-1166 in Twig
Summary
by MITRE
Twig webmail system does not properly set the "vhosts" variable if it is not configured on the site, which allows remote attackers to insert arbitrary PHP (PHP3) code by specifying an alternate vhosts as an argument to the index.php3 program.
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Analysis
by VulDB Data Team • 05/28/2018
The vulnerability identified as CVE-2000-1166 resides within the Twig webmail system, a widely used email client interface that was prevalent in the late 1990s and early 2000s. This flaw represents a classic case of improper input validation and insecure parameter handling that could lead to arbitrary code execution. The vulnerability specifically manifests when the system fails to properly initialize or validate the "vhosts" variable, which is intended to control virtual host configurations for the webmail interface. When this variable is not explicitly configured within the system, the application does not adequately sanitize user input, creating a path for malicious actors to manipulate the application's behavior through crafted HTTP requests.
The technical exploitation of this vulnerability occurs through the manipulation of the index.php3 program's argument handling mechanism. Attackers can specify an alternate vhosts parameter as an argument, which the system then processes without proper validation or sanitization. This misconfiguration allows for the injection of arbitrary PHP code, effectively bypassing the intended security boundaries of the webmail system. The vulnerability stems from a fundamental flaw in the application's input processing logic where user-supplied parameters are directly incorporated into the execution flow without proper filtering or validation. This type of vulnerability is categorized under CWE-20 as "Improper Input Validation" and represents a variant of code injection attacks that can be classified under the ATT&CK framework as T1190 "Exploit Public-Facing Application" and T1059.007 "Command and Scripting Interpreter: PHP."
The operational impact of this vulnerability is significant as it provides remote attackers with the ability to execute arbitrary code on the affected server, potentially leading to complete system compromise. Once exploited, attackers can gain unauthorized access to the webmail system's underlying resources, potentially accessing email accounts, user credentials, and sensitive data stored within the system. The vulnerability affects not only the confidentiality of email communications but also the integrity and availability of the entire webmail infrastructure. Given that Twig was commonly deployed in shared hosting environments and enterprise email systems, the potential attack surface was extensive, making this vulnerability particularly dangerous. The impact extends beyond simple code execution to include potential privilege escalation and persistence mechanisms that could allow attackers to maintain long-term access to compromised systems. Organizations running vulnerable versions of Twig faced the risk of data breaches, unauthorized access to email communications, and potential use as a foothold for further attacks within their network infrastructure.
Mitigation strategies for CVE-2000-1166 focus on both immediate patching and architectural improvements. The most effective solution involves applying the official security patches released by the Twig development team, which would properly initialize and validate the vhosts variable before processing user input. System administrators should also implement input validation mechanisms that sanitize all user-supplied parameters, particularly those that control application behavior or resource access. Network-level mitigations include implementing proper access controls and firewall rules to limit access to the index.php3 endpoint, while application-level protections involve configuring the system to properly initialize all variables and validate input parameters before processing. The vulnerability highlights the importance of proper secure coding practices and input validation, aligning with industry standards such as the OWASP Top Ten and NIST cybersecurity guidelines. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for suspicious parameter manipulation attempts. Regular security audits and vulnerability assessments should be conducted to identify similar input validation flaws in legacy applications, as this vulnerability demonstrates how seemingly minor configuration issues can lead to critical security breaches. The incident underscores the necessity of comprehensive security testing, including parameter validation and code injection testing, before deploying web applications in production environments.