CVE-2016-5099 in phpMyAdmin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in phpMyAdmin 4.4.x before 4.4.15.6 and 4.6.x before 4.6.2 allows remote attackers to inject arbitrary web script or HTML via special characters that are mishandled during double URL decoding.
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Analysis
by VulDB Data Team • 08/22/2022
The CVE-2016-5099 vulnerability represents a critical cross-site scripting flaw discovered in phpMyAdmin versions 4.4.x prior to 4.4.15.6 and 4.6.x prior to 4.6.2. This vulnerability stems from improper handling of special characters during double URL decoding processes, creating a pathway for remote attackers to execute malicious web scripts or HTML code within the context of affected systems. The flaw specifically manifests when the application processes URL-encoded parameters that undergo double decoding, allowing attackers to bypass security measures and inject malicious payloads. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is a fundamental web application security weakness that enables attackers to inject client-side scripts into web pages viewed by other users. The vulnerability operates at the application layer and can be exploited through various attack vectors including web browsers, making it particularly dangerous for database management interfaces that are frequently accessed by administrators and users with elevated privileges.
The technical exploitation of this vulnerability occurs when phpMyAdmin processes parameters that contain special characters which are subjected to double URL decoding operations. During this process, the application fails to properly sanitize or validate input data that has already been URL decoded once, allowing malicious payloads to persist and execute when the application renders the affected pages. Attackers can craft specially formatted URLs containing encoded malicious scripts that, when processed through the double decoding mechanism, remain intact and are subsequently executed within the victim's browser context. This particular flaw demonstrates a classic case of improper input validation and output encoding, where the application assumes that URL decoding operations are sufficient to neutralize malicious content without proper additional sanitization. The vulnerability is particularly concerning because phpMyAdmin is widely used for database administration tasks, making it a prime target for attackers seeking to compromise database servers and potentially gain access to sensitive information stored within them.
The operational impact of CVE-2016-5099 extends beyond simple script injection, as it can potentially enable attackers to perform session hijacking, steal user credentials, redirect users to malicious sites, or execute more sophisticated attacks such as privilege escalation within the database environment. When administrators or users access the vulnerable phpMyAdmin interface, they become potential victims of the XSS attack, with their browsers executing malicious scripts that can capture session cookies, redirect to phishing sites, or even modify database content if the application has sufficient privileges. The vulnerability's exploitation can lead to complete compromise of the database management system, especially when combined with other attack techniques or when administrators have elevated access rights. Organizations running vulnerable versions of phpMyAdmin face significant risk of data breaches, unauthorized database access, and potential lateral movement within their network infrastructure, as the compromised interface can serve as a foothold for more extensive attacks. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1566.001 for Phishing, as it enables attackers to execute malicious code through web-based delivery mechanisms and user interaction.
Mitigation strategies for CVE-2016-5099 primarily involve immediate patching of affected phpMyAdmin installations to versions 4.4.15.6 or 4.6.2 and later, which contain the necessary fixes for proper double URL decoding handling. Organizations should also implement additional security measures including input validation and output encoding for all user-supplied data, proper URL decoding procedures, and regular security assessments of web applications. Network-based mitigations such as web application firewalls can provide additional protection layers, though they are not substitutes for proper patching. Security teams should also conduct regular training on secure coding practices and implement proper access controls to limit exposure of vulnerable interfaces. The vulnerability highlights the importance of thorough input validation and the need for applications to properly handle encoding and decoding operations, particularly when dealing with web-based parameters that may contain special characters. Organizations should also establish robust patch management processes to ensure timely deployment of security updates and maintain visibility into their application security posture through continuous monitoring and vulnerability assessment activities.