CVE-2023-21920 in MySQL Server
Summary
by MITRE • 04/18/2023
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are 8.0.32 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 • 05/08/2025
The vulnerability identified as CVE-2023-21920 resides within the MySQL Server optimizer component of Oracle MySQL, affecting versions 8.0.32 and earlier. This represents a significant availability risk that can be exploited by attackers with high privileges and network access through multiple protocols. The vulnerability manifests as a flaw in how the server processes certain optimizer operations, leading to potential system instability and denial of service conditions. The CVSS score of 4.9 indicates a moderate severity impact, with the primary concern being availability rather than confidentiality or integrity.
The technical nature of this vulnerability stems from improper handling within the query optimizer module that processes SQL statements and generates execution plans for database operations. When specific complex queries or optimizer-related operations are executed against the affected MySQL server, the optimizer component fails to properly manage memory or execution flow, resulting in system crashes or hangs. This type of flaw typically involves buffer overflows, memory corruption, or improper state management within the database engine's internal processing mechanisms. The vulnerability's classification as easily exploitable suggests that the attack vector requires minimal sophistication and can be triggered through standard database operations.
Operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire database infrastructure reliability. A successful exploitation can result in complete denial of service conditions where the MySQL server becomes unavailable to legitimate users and applications. This can cascade into broader system failures, particularly in environments where database availability is critical for business operations. The vulnerability affects high-privileged attackers who can leverage network access to directly interact with the database server, making it particularly concerning for environments with less stringent access controls or where administrative privileges are compromised. Organizations may experience extended downtime, data access interruptions, and potential business continuity impacts.
Mitigation strategies for CVE-2023-21920 should prioritize immediate patching of affected MySQL server instances to version 8.0.33 or later, which contains the necessary fixes for the optimizer component. Network segmentation and access controls should be reinforced to limit privileged access to database servers, implementing the principle of least privilege for database administrators. Monitoring systems should be enhanced to detect unusual patterns in database server behavior or frequent restarts that might indicate exploitation attempts. Additionally, implementing database activity monitoring and logging can help identify potential attack vectors before they result in service disruption. Organizations should also consider implementing redundant database systems and failover mechanisms to minimize the impact of potential denial of service conditions. This vulnerability aligns with CWE-121 and CWE-122 categories related to buffer overflow conditions and heap-based buffer overflows, while the attack pattern corresponds to ATT&CK techniques involving service stoppage and availability disruption.