CVE-2021-2203 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 • 08/18/2025
The vulnerability identified as CVE-2021-2203 represents a critical availability issue within Oracle MySQL Server's optimizer component, affecting versions 8.0.23 and earlier. This flaw resides in 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 MySQL server operations. The CVSS score of 4.9 reflects the significant availability impact, specifically targeting the ability to cause complete denial of service through hangs or repeated crashes, which fundamentally undermines the database server's operational integrity.
The technical nature of this vulnerability stems from improper handling within the MySQL Server's optimizer module, where specific query patterns or execution paths can trigger memory corruption or resource management failures. This flaw operates at a low-level system component that processes database operations, making it particularly dangerous as it can be triggered through multiple network protocols including TCP/IP connections to the MySQL service port. The high privilege requirement suggests that the attack vector typically involves authenticated users who already possess administrative or sufficient access rights to the database system, though the network accessibility allows for remote exploitation.
From an operational perspective, successful exploitation of CVE-2021-2203 can result in complete service disruption for database applications relying on the affected MySQL versions. The vulnerability's ability to cause repeated crashes or system hangs means that database servers could become unavailable for extended periods, potentially affecting business-critical applications that depend on continuous database access. This type of denial of service attack can be particularly damaging in production environments where database uptime is essential for business operations, potentially leading to financial losses and service degradation. The vulnerability's impact extends beyond simple unavailability as it can affect database consistency and recovery operations during crash scenarios.
Organizations should prioritize immediate patching of affected MySQL Server installations to address this vulnerability, as no effective workarounds exist for the underlying optimizer flaw. The recommended mitigation strategy involves upgrading to MySQL Server version 8.0.24 or later, which contains the necessary fixes for the optimizer component. Security administrators should also implement network segmentation and access controls to limit exposure, though these measures do not eliminate the risk entirely. Monitoring systems should be configured to detect unusual patterns of service disruption or crash events that might indicate exploitation attempts. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and may map to ATT&CK technique T1499.004 for network denial of service attacks, emphasizing the importance of maintaining updated database server software and implementing comprehensive security monitoring protocols.