CVE-2021-2383 in MySQL Server
Summary
by MITRE • 07/21/2021
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.25 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 • 07/25/2021
The vulnerability identified as CVE-2021-2383 represents a significant availability risk within Oracle MySQL Server's optimizer component, affecting versions 8.0.25 and earlier. This flaw exists within the server's query optimization engine, which is responsible for determining the most efficient execution path for database queries. The vulnerability's classification as easily exploitable indicates that attackers with high privileges and network access can leverage this weakness to disrupt database operations. The CVSS score of 4.9 reflects the moderate severity of the availability impact, though the potential for complete denial of service makes this threat particularly concerning for production environments. The vulnerability's accessibility via multiple protocols suggests a broad attack surface that could be exploited through various network entry points.
The technical implementation of this vulnerability stems from improper handling within the MySQL Server's optimizer module, which processes complex query execution plans. When specific query patterns are executed against the affected server, the optimizer fails to properly manage memory allocation or execution flow, leading to system instability. This flaw allows an authenticated attacker with sufficient privileges to craft malicious queries that trigger a condition causing the MySQL server process to either hang indefinitely or crash repeatedly. The nature of the failure results in a complete denial of service scenario where legitimate database operations cannot proceed, effectively rendering the database server unusable for its intended purpose. The vulnerability demonstrates characteristics consistent with memory management issues and could potentially be categorized under CWE-129 or CWE-131 depending on the specific implementation details of the memory handling error.
The operational impact of CVE-2021-2383 extends beyond simple service disruption to encompass broader business continuity concerns for organizations relying on MySQL databases. When exploited successfully, the vulnerability can cause cascading failures throughout database-dependent applications, potentially affecting multiple services that depend on the compromised server. The high privilege requirement suggests that this vulnerability is most likely exploited by insiders or through compromised administrative accounts rather than external attackers, though the network accessibility aspect means that any attacker who gains elevated privileges could leverage this weakness. Organizations using MySQL 8.0.25 or earlier versions face significant risk without proper mitigation, as the vulnerability can be triggered through standard database operations and does not require specialized tools or techniques to exploit.
Mitigation strategies for CVE-2021-2383 should prioritize immediate patching of affected MySQL installations to version 8.0.26 or later, where Oracle has addressed the underlying optimizer issue. System administrators should implement network segmentation and access controls to limit privileged access to database servers, reducing the attack surface for potential exploitation. Monitoring should focus on unusual query patterns or repeated connection failures that might indicate exploitation attempts, with particular attention to queries involving complex joins or subqueries that could trigger the optimizer bug. The vulnerability's alignment with ATT&CK technique T1499.004 (Authorization Tokens) suggests that organizations should also review their privilege management and access control policies to ensure that administrative accounts are properly secured and monitored for anomalous activity. Additionally, implementing database activity monitoring solutions can help detect and alert on suspicious query execution patterns that might indicate exploitation attempts.