CVE-2021-2170 in MySQL Server
Summary
by MITRE • 04/23/2021
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.23 and prior. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server. CVSS 3.1 Base Score 4.9 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H).
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Analysis
by VulDB Data Team • 04/26/2021
The vulnerability identified as CVE-2021-2170 resides within the MySQL Server optimizer component of Oracle MySQL, affecting versions 8.0.23 and earlier. This represents a significant security weakness that operates at the core of database query processing, where the optimizer is responsible for determining the most efficient execution plan for SQL queries. The flaw manifests in how the server handles specific query optimization scenarios, creating a pathway for malicious actors to disrupt normal database operations through carefully crafted inputs that exploit the optimizer's handling of complex query structures.
This vulnerability operates with a CVSS score of 4.9, classified as having high privilege requirements but low attack complexity, making it particularly concerning for environments where database administrators maintain elevated access levels. The attack vector requires network access via multiple protocols, indicating that the vulnerability can be exploited through various communication channels that MySQL typically supports including TCP/IP connections, Unix domain sockets, and named pipes. The fact that this is an easily exploitable vulnerability means that skilled attackers can potentially trigger the flaw with minimal effort once they have achieved the necessary privileged access level, typically requiring administrative or high-privilege database user credentials.
The operational impact of CVE-2021-2170 is severe, as successful exploitation results in a complete denial of service condition that can cause the MySQL server to hang or repeatedly crash. This availability impact represents a critical concern for database-dependent applications, as database downtime can cascade into broader system failures affecting business operations, data integrity, and user access. The vulnerability's potential to cause frequently repeatable crashes means that even a single successful exploitation attempt can result in sustained service disruption, requiring system administrators to perform manual intervention to restore normal operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a classic example of how optimization algorithms in database systems can contain flaws that lead to system instability. The ATT&CK framework categorizes this vulnerability under T1499.004, specifically targeting the availability of services through resource exhaustion or system instability, making it particularly dangerous in enterprise environments where database availability is critical for business continuity. Organizations should implement immediate mitigation strategies including patching to the latest MySQL 8.0 versions, network segmentation to limit access to database servers, and implementing monitoring solutions to detect unusual patterns of database crashes or connection failures that might indicate exploitation attempts.
The vulnerability demonstrates the inherent complexity of database optimization engines and how sophisticated query processing algorithms can contain subtle flaws that are difficult to detect during normal testing cycles. Database administrators should also consider implementing additional security controls such as connection throttling, query execution limits, and comprehensive logging of database activities to detect potential exploitation attempts. Regular security assessments of database systems, including vulnerability scanning and penetration testing, are essential to identify similar weaknesses in database management systems that could provide similar attack vectors for compromising system availability and integrity.