CVE-2020-14809 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 • 08/17/2025
The vulnerability identified as CVE-2020-14809 represents a significant availability risk within Oracle MySQL Server versions 8.0.21 and earlier, specifically affecting the Server: Optimizer component. This flaw demonstrates how database optimization routines can become attack vectors when improperly handled, creating a scenario where a high-privileged attacker with network access can exploit the system to cause complete denial of service conditions. The vulnerability operates through multiple network protocols, making it particularly dangerous as it can be leveraged across various attack vectors without requiring specialized tools or conditions.
The technical nature of this vulnerability stems from improper handling within the MySQL Server optimizer module, which is responsible for determining the most efficient execution plans for database queries. When specific query patterns or optimization scenarios are processed, the optimizer fails to properly validate or handle certain inputs, leading to memory corruption or resource exhaustion conditions. This flaw operates at a fundamental level of database operation where query optimization decisions directly impact system stability and resource allocation, making it particularly dangerous for production environments where database performance and availability are critical. The vulnerability's classification under CWE-121 (Stack-based Buffer Overflow) and CWE-122 (Heap-based Buffer Overflow) indicates potential memory corruption mechanisms that can lead to system instability.
The operational impact of CVE-2020-14809 extends beyond simple service disruption to potentially compromise entire database infrastructure availability. Successful exploitation can result in complete database server crashes that require manual intervention to restore service, leading to extended downtime and potential data loss scenarios. Organizations relying on MySQL for mission-critical applications face significant risk as this vulnerability can be triggered through normal database operations, meaning that legitimate users could inadvertently cause system crashes during routine database interactions. The CVSS 3.1 Base Score of 4.9 reflects the moderate to high severity impact on system availability, while the attack complexity requirement of low access control and high privileges indicates that this vulnerability targets the database server's internal processing rather than external network interfaces.
Mitigation strategies for this vulnerability should focus on immediate patch management and system hardening measures. Organizations must prioritize updating to MySQL Server versions 8.0.22 or later where this vulnerability has been addressed through proper input validation and resource management within the optimizer component. Network segmentation and access control measures should be implemented to limit the attack surface, ensuring that only authorized personnel can access database servers with elevated privileges. Additionally, monitoring systems should be enhanced to detect unusual query patterns that might indicate exploitation attempts, and regular database server health checks should be implemented to identify potential instability before complete system failures occur. The ATT&CK framework categorizes this vulnerability under T1489 (Service Stop) and T1070 (Indicator Removal on Host) as attackers may attempt to disrupt database services and potentially cover their tracks through system manipulation. Organizations should also implement database activity monitoring solutions that can detect anomalous query execution patterns that might indicate exploitation attempts, while maintaining regular backup and recovery procedures to minimize downtime impact.