CVE-2021-2299 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 • 04/26/2021
The vulnerability identified as CVE-2021-2299 represents a critical availability threat within Oracle MySQL Server's optimizer component, affecting versions 8.0.23 and earlier. This flaw exists within the server's query optimization logic where specific malformed queries can trigger unexpected behavior in the database engine's execution path. The vulnerability's classification as easily exploitable indicates that attackers with high privileges and network access can leverage this weakness through multiple protocols including TCP/IP connections to the MySQL service. The attack vector requires minimal complexity to execute, making it particularly dangerous in environments where privileged network access is possible.
The technical implementation of this vulnerability stems from insufficient input validation within the MySQL Server's optimizer module. When processing certain complex SQL queries that involve specific join operations or subquery structures, the optimizer fails to properly handle edge cases in query execution planning. This leads to memory corruption or internal state inconsistencies that cause the MySQL daemon to enter an unrecoverable state. The flaw specifically manifests during query compilation and execution phases where the optimizer attempts to generate execution plans for queries containing particular combinations of operators and data structures. The vulnerability's design flaw can be categorized under CWE-129, representing an insufficient input validation issue that allows for arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete denial of service conditions that can severely impact database availability. Successful exploitation results in the MySQL Server process becoming unresponsive or crashing repeatedly, forcing administrators to manually restart the service and potentially causing data loss or transaction failures. In production environments, this vulnerability can compromise business continuity and data integrity, particularly when the database serves critical applications that cannot tolerate extended downtime. The availability impact is rated at CVSS 3.1 score of 4.9, indicating a moderate to high risk of system unavailability that can affect multiple concurrent database users and applications simultaneously.
Organizations should implement immediate mitigations including applying the latest Oracle MySQL patches and updates that address this specific optimizer flaw. System administrators should consider implementing network segmentation and access controls to limit privileged network access to MySQL services, reducing the attack surface for potential exploitation. The vulnerability aligns with ATT&CK technique T1499.004 which involves network denial of service attacks targeting database services. Additionally, implementing monitoring solutions that detect unusual MySQL process behavior or frequent service restarts can provide early warning of exploitation attempts. Organizations should also review their access control policies to ensure that only necessary administrative accounts have network access to database servers, reducing the likelihood of privilege escalation attacks that could leverage this vulnerability. The recommended approach includes comprehensive testing of patches in staging environments before deployment to production systems to avoid unexpected compatibility issues.