CVE-2016-6623 in phpMyAdmin
Summary
by MITRE
An issue was discovered in phpMyAdmin. An authorized user can cause a denial-of-service (DoS) attack on a server by passing large values to a loop. All 4.6.x versions (prior to 4.6.4), 4.4.x versions (prior to 4.4.15.8), and 4.0.x versions (prior to 4.0.10.17) are affected.
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Analysis
by VulDB Data Team • 06/23/2019
The vulnerability identified as CVE-2016-6623 represents a critical denial-of-service weakness in phpMyAdmin that affects multiple version branches including 4.6.x prior to 4.6.4, 4.4.x prior to 4.4.15.8, and 4.0.x prior to 4.0.10.17. This flaw enables authenticated users to exploit a loop mechanism within the application by providing excessively large values, thereby causing the server to become unresponsive or crash. The vulnerability stems from inadequate input validation and loop boundary checking within the application's code execution flow, creating a scenario where legitimate users with valid credentials can disrupt service availability. The affected versions of phpMyAdmin are widely deployed across various hosting environments and database management systems, making this vulnerability particularly concerning for organizations relying on these platforms for database administration tasks.
The technical implementation of this vulnerability involves a specific code path where phpMyAdmin processes user-supplied parameters through iterative loops without proper bounds checking or input sanitization. When an authenticated user submits large numerical values to certain loop parameters, the application enters an extended processing cycle that consumes excessive system resources including cpu cycles and memory allocation. This behavior manifests as a resource exhaustion attack that can be executed remotely by any user with valid login credentials, effectively allowing privilege escalation from authenticated user status to service disruption capability. The flaw operates at the application layer and can be classified under CWE-770, which addresses allocation of resources without limits or throttling, making it particularly dangerous in multi-tenant hosting environments where a single compromised account could affect multiple users. The vulnerability directly relates to ATT&CK technique T1499.004 which involves network denial of service attacks through resource exhaustion.
The operational impact of CVE-2016-6623 extends beyond simple service disruption to encompass broader security implications for database management environments. Organizations using vulnerable versions of phpMyAdmin face potential business continuity issues as attackers can systematically consume server resources without requiring elevated privileges or specialized tools. The vulnerability affects not only individual server performance but can also impact database availability for legitimate users, potentially leading to data access delays or complete unavailability of database services. System administrators must consider that this vulnerability can be exploited in automated attacks, where malicious actors could create scripts to repeatedly trigger the DoS condition, amplifying the impact on server resources. The vulnerability's exploitation requires minimal technical skill, making it accessible to attackers with basic knowledge of phpMyAdmin's interface and parameter handling mechanisms.
Mitigation strategies for CVE-2016-6623 primarily focus on immediate software updates and implementation of access controls. Organizations should prioritize upgrading to patched versions of phpMyAdmin, specifically version 4.6.4 or higher for 4.6.x releases, 4.4.15.8 or higher for 4.4.x releases, and 4.0.10.17 or higher for 4.0.x releases. Additionally, implementing rate limiting mechanisms and input validation controls can provide temporary protection while updates are being deployed. Network-level mitigations including firewall rules and intrusion detection systems can help identify and block suspicious parameter patterns that may indicate exploitation attempts. Security teams should also consider implementing monitoring for unusual resource consumption patterns that could indicate successful exploitation of this vulnerability. The implementation of principle of least privilege access controls, where users are granted only necessary permissions, reduces the attack surface as exploitation requires authenticated access. Regular vulnerability assessments and security audits should be conducted to identify and remediate similar issues within the broader application ecosystem, particularly focusing on loop constructs and resource allocation patterns that may present similar vulnerabilities.