CVE-2016-9856 in phpMyAdmin
Summary
by MITRE
An XSS issue was discovered in phpMyAdmin because of an improper fix for CVE-2016-2559 in PMASA-2016-10. This issue is resolved by using a copy of a hash to avoid a race condition. All 4.6.x versions (prior to 4.6.5), 4.4.x versions (prior to 4.4.15.9), and 4.0.x versions (prior to 4.0.10.18) are affected.
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Analysis
by VulDB Data Team • 06/23/2019
The vulnerability identified as CVE-2016-9856 represents a regression in phpMyAdmin's security implementation that emerged from an inadequate patch for a previously resolved cross-site scripting flaw. This issue specifically affects phpMyAdmin versions within the 4.0.x, 4.4.x, and 4.6.x release lines, with the affected versions being those prior to the respective security patches 4.0.10.18, 4.4.15.9, and 4.6.5. The vulnerability stems from an improper fix for CVE-2016-2559, which demonstrates how security patches can sometimes introduce new weaknesses when not carefully implemented. The root cause lies in the application's handling of hash references within its session management system, where a race condition could occur during concurrent access scenarios, potentially allowing malicious actors to inject and execute arbitrary JavaScript code in the context of a victim's browser session.
The technical implementation flaw manifests in how phpMyAdmin manages session data and hash structures during concurrent user interactions. When multiple users access the application simultaneously, the improper fix for CVE-2016-2559 created a scenario where a hash reference could be modified or accessed concurrently, leading to a race condition that undermines the intended security protections. This race condition occurs because the original fix attempted to address the vulnerability by creating a copy of a hash, but this approach was insufficient or incorrectly implemented. The vulnerability falls under the CWE-362 category of race conditions, specifically manifesting as a timing vulnerability where the order of operations between hash manipulation and session validation creates an exploitable window. The improper handling of hash references in a multi-threaded or concurrent environment allows attackers to potentially manipulate session data and execute malicious scripts.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to hijack user sessions and potentially gain unauthorized access to database systems managed through phpMyAdmin. When exploited, the XSS vulnerability could allow an attacker to inject malicious JavaScript that executes in the victim's browser context, potentially leading to session theft, data exfiltration, or privilege escalation within the database environment. The vulnerability affects database administrators and users who rely on phpMyAdmin for database management, making it particularly dangerous in environments where the application serves as a critical interface for database operations. Attackers could leverage this vulnerability to steal session cookies, execute commands on behalf of authenticated users, or redirect victims to malicious websites that could further compromise the security posture of the affected systems.
Mitigation strategies for CVE-2016-9856 require immediate patching of affected phpMyAdmin installations to the recommended secure versions that properly address the race condition in hash handling. Organizations should prioritize updating their phpMyAdmin deployments across all affected branches, ensuring that the updated versions contain the corrected implementation of the hash copy mechanism that prevents the race condition. System administrators should also implement network-level monitoring to detect potential exploitation attempts and consider additional security controls such as web application firewalls that can detect and block malicious script injection attempts. The vulnerability highlights the importance of thorough testing of security patches in production environments and demonstrates how seemingly minor implementation details in concurrent programming can have significant security implications. Security teams should also review their incident response procedures to ensure they can quickly identify and respond to potential exploitation attempts of this class of vulnerability, which may manifest as unusual session behavior or suspicious user activity patterns.