CVE-2020-14845 in MySQL Server
Summary
by MITRE • 10/21/2020
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.21 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 • 11/24/2020
The vulnerability identified as CVE-2020-14845 resides within the MySQL Server optimizer component of Oracle MySQL, affecting versions 8.0.21 and earlier. This represents a critical availability-focused weakness that demonstrates how seemingly routine database operations can be weaponized to disrupt service availability. The vulnerability operates within the server's query optimization logic, specifically targeting how the system processes certain complex queries that involve multiple table joins and subqueries. The flaw manifests when the optimizer encounters specific combinations of SQL constructs that trigger an internal memory management issue during query execution planning.
The technical nature of this vulnerability stems from improper handling of memory allocation and deallocation within the optimizer's query plan generation process. When processing certain complex queries that involve nested subqueries, multiple join operations, and specific aggregate functions, the MySQL server's optimizer fails to properly manage memory resources, leading to a condition where memory corruption occurs during the query execution phase. This memory corruption ultimately results in the server becoming unresponsive or crashing entirely, presenting a complete denial of service scenario. The vulnerability is classified as easily exploitable due to the minimal privileges required for exploitation, specifically requiring only high-privileged network access through multiple protocols including TCP/IP and Unix sockets. The attack vector demonstrates how an attacker with sufficient privileges to establish network connections to the MySQL server can trigger this condition through carefully crafted SQL queries.
From an operational impact perspective, this vulnerability presents significant risk to database availability and business continuity. The complete denial of service condition means that legitimate database users cannot access critical applications that depend on MySQL functionality, potentially affecting entire business operations. The vulnerability's CVSS score of 4.9 indicates a moderate severity impact, but the availability impact rating of high means that organizations face substantial operational disruption. The vulnerability's characteristics make it particularly dangerous in production environments where database uptime is critical, as the crash condition can occur repeatedly with the same query pattern, making it difficult to recover from without manual intervention. Organizations running affected MySQL versions face potential data unavailability, service interruptions, and the need for immediate patching or workaround implementations.
The vulnerability aligns with CWE-129, which addresses improper validation of array index bounds, and demonstrates how memory management issues in database query optimizers can lead to system instability. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service and T1566.001 for spearphishing via email, as attackers could potentially use this vulnerability to disrupt services during targeted attacks. The exploitation process requires minimal technical sophistication but demands knowledge of MySQL query structures and the ability to craft specific SQL statements that trigger the memory corruption condition. Organizations should implement immediate patch management strategies to address this vulnerability, as Oracle released patches for this issue in their regular update cycles. Additionally, implementing network segmentation and access controls to limit high-privilege network access to MySQL servers can provide defense-in-depth measures while awaiting patch deployment. The vulnerability serves as a reminder of the critical importance of proper memory management in database server components and the potential for seemingly benign query optimization logic to create catastrophic system failures.