CVE-2021-2020 in MySQL Server
Summary
by MITRE • 01/20/2021
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.20 and prior. Easily exploitable vulnerability allows low 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 6.5 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
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Analysis
by VulDB Data Team • 02/17/2021
The vulnerability identified as CVE-2021-2020 represents a critical availability threat within Oracle MySQL Server's optimizer component, affecting versions 8.0.20 and earlier. This flaw resides in the server's query optimization engine, which is responsible for determining the most efficient execution plan for database queries. The vulnerability's classification as easily exploitable indicates that attackers with minimal privileges and network access can leverage this weakness to disrupt database operations. The attack vector requires network connectivity through multiple protocols, making it accessible to a broad range of potential threat actors who may not possess elevated system privileges.
The technical nature of this vulnerability stems from improper handling within the MySQL Server's optimizer module, which processes complex database queries and determines execution strategies. When exploited, the flaw triggers a condition that causes the MySQL Server process to enter a state of indefinite hanging or repeated crashes, effectively rendering the database service unavailable to legitimate users and applications. This behavior constitutes a complete denial of service scenario where the database server becomes non-responsive and requires manual intervention or restart to restore functionality. The vulnerability's impact on availability is particularly severe as database services form the backbone of most enterprise applications, making this weakness especially dangerous in production environments where uptime is critical.
From an operational standpoint, this vulnerability creates significant risk for organizations relying on MySQL databases, particularly those running affected versions. The low privilege requirement means that even users with minimal database permissions can potentially disrupt critical services, making it a valuable target for both external attackers seeking to cause disruption and internal malicious actors. The complete DOS condition can result in extended downtime for applications dependent on the affected database, potentially causing cascading failures throughout connected systems. The CVSS 3.1 score of 6.5 reflects the balance between the ease of exploitation and the high availability impact, while the vector AV:N/AC:L/PR:L indicates that network-based attacks requiring only low privileges can successfully compromise the system.
Organizations should prioritize immediate remediation by upgrading to MySQL Server version 8.0.21 or later, which contains the necessary patches to address this vulnerability. System administrators should also implement network segmentation and access controls to limit exposure, particularly by restricting unnecessary network access to database servers. The vulnerability aligns with CWE-121, which describes buffer overflow conditions, and may relate to ATT&CK technique T1499.004 for network disruption attacks. Additional mitigations include monitoring database server processes for unusual behavior patterns, implementing intrusion detection systems, and conducting regular vulnerability assessments to identify and remediate similar issues. Organizations should also review their incident response procedures to ensure rapid detection and recovery from potential exploitation attempts.