CVE-2021-2418 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-2021-2418 represents a critical availability threat within Oracle MySQL Server's optimizer component, specifically affecting versions 8.0.25 and earlier. This weakness resides in the server's query optimization engine which is responsible for determining the most efficient execution plan for database queries. The vulnerability manifests when the optimizer encounters specific query patterns that trigger an abnormal memory handling behavior, leading to system instability. The flaw is classified as easily exploitable due to the minimal prerequisites required for successful exploitation, making it particularly dangerous in environments where attackers may have elevated privileges or network access to the database server.
The technical nature of this vulnerability stems from improper handling of memory allocation and deallocation within the MySQL Server's optimizer module. When processing certain complex queries or specific combinations of SQL operations, the optimizer fails to properly manage memory resources, causing memory corruption or exhaustion that ultimately results in server crashes. This memory management failure can be triggered through multiple network protocols including TCP/IP connections, making the attack surface broader than typical database vulnerabilities. The vulnerability operates at a low-level system component, bypassing many standard security controls and directly impacting the server's operational stability. According to CWE classification, this represents a memory error vulnerability (CWE-129) with specific characteristics related to improper handling of memory allocation in database query processing systems.
The operational impact of CVE-2021-2418 extends beyond simple service disruption to potentially severe business consequences for organizations relying on MySQL infrastructure. Successful exploitation can result in complete denial of service conditions where the MySQL Server becomes unavailable for legitimate database operations, affecting all applications and services dependent on database connectivity. The vulnerability's ability to cause frequent repeatable crashes means that even brief attacks can result in prolonged downtime, potentially leading to data loss, transaction failures, and significant financial impact. Organizations with high availability requirements face particular risk as the vulnerability can be leveraged to create sustained service interruptions that may not be immediately apparent to administrators. The CVSS 3.1 score of 4.9 reflects the moderate to high severity impact on availability, with the high privilege requirement and network access vector indicating that this vulnerability is most dangerous in environments where attackers have already gained significant access rights.
Mitigation strategies for CVE-2021-2418 should prioritize immediate patch management with the release of MySQL Server version 8.0.26 or later, which contains the necessary fixes for the optimizer memory handling issue. Organizations should implement network segmentation to limit access to MySQL servers, ensuring that only authorized systems can establish connections to database services. Access controls must be strictly enforced through proper authentication mechanisms and privilege management to prevent unauthorized users from exploiting the vulnerability. Monitoring systems should be enhanced to detect unusual patterns of database connection attempts or query execution that might indicate exploitation attempts. The vulnerability aligns with ATT&CK techniques related to privilege escalation and denial of service, making it important for security teams to monitor for these specific attack patterns. Additionally, implementing database activity monitoring and log analysis can help detect potential exploitation attempts before they result in service disruption. Regular vulnerability assessments and penetration testing should be conducted to identify and remediate similar issues within the database infrastructure.