CVE-2016-9850 in phpMyAdmin
Summary
by MITRE
An issue was discovered in phpMyAdmin. Username matching for the allow/deny rules may result in wrong matches and detection of the username in the rule due to non-constant execution time. 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.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/05/2022
The vulnerability identified as CVE-2016-9850 represents a critical security flaw in phpMyAdmin that affects authentication mechanisms through improper handling of username matching in allow/deny access control rules. This issue specifically targets the way the application processes user credentials when evaluating access control lists, creating potential pathways for unauthorized access to database management interfaces. The vulnerability stems from the implementation of username matching algorithms that exhibit variable execution time characteristics, which can be exploited to bypass intended access restrictions through timing-based attacks.
The technical root cause of this vulnerability lies in the non-constant time execution of username comparison operations within phpMyAdmin's authentication subsystem. When evaluating allow/deny rules, the application performs string comparisons that do not execute in constant time regardless of input length or complexity. This timing variation creates observable differences in processing duration that can be measured and exploited by attackers to infer information about valid usernames or to bypass authentication controls entirely. The vulnerability affects multiple version streams including 4.6.x prior to 4.6.5, 4.4.x prior to 4.4.15.9, and 4.0.x prior to 4.0.10.18, indicating a widespread issue across the phpMyAdmin codebase that persisted across several major releases.
This vulnerability directly impacts the integrity of access control mechanisms within phpMyAdmin, potentially allowing attackers to gain unauthorized access to database management interfaces. The operational impact extends beyond simple privilege escalation as the timing-based nature of the flaw enables attackers to perform username enumeration attacks, where they can determine valid usernames through careful analysis of response times. This creates a significant risk for database administrators who rely on phpMyAdmin for their database management tasks, as compromised access could lead to data exposure, manipulation, or complete system compromise. The vulnerability operates at the application layer and can be exploited remotely without requiring prior authentication, making it particularly dangerous in environments where phpMyAdmin is exposed to untrusted networks.
The security implications of CVE-2016-9850 align with CWE-203, which addresses "Observable Timing Discrepancy" in security-sensitive code implementations. This classification indicates that the vulnerability represents a fundamental flaw in how the application handles sensitive operations that can be exploited through timing analysis. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and privilege escalation, specifically targeting the T1110.003 sub-technique for "Brute Force" and T1562.001 for "Disable or Modify Tools" through potential unauthorized access to database management interfaces. The flaw demonstrates how seemingly benign implementation details in authentication systems can create exploitable weaknesses that undermine the entire security architecture. Organizations should prioritize immediate patching of affected versions to prevent exploitation and implement additional monitoring for unusual authentication patterns that might indicate timing-based attacks. The vulnerability serves as a reminder of the critical importance of constant-time algorithm implementations in security-sensitive contexts and the need for comprehensive security testing that includes timing analysis.