CVE-2021-2387 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-2021-2387 resides within the MySQL Server optimizer component of Oracle MySQL, affecting versions 8.0.25 and earlier. This represents a significant security weakness that operates at the core of database query processing, where the optimizer is responsible for determining the most efficient execution plan for SQL queries. The vulnerability's classification as easily exploitable indicates that attackers with high privileges and network access can leverage this flaw without requiring extensive technical expertise or specialized tools. The attack surface extends across multiple network protocols, making the vulnerability particularly dangerous as it can be accessed through various communication channels that MySQL supports. This characteristic aligns with the Common Weakness Enumeration (CWE) classification for software vulnerabilities that allow unauthorized access to system resources through network-based attacks.
The technical nature of this vulnerability manifests as a condition that can cause complete denial of service attacks against MySQL Server instances. When successfully exploited, the vulnerability enables attackers to force the database server into a state where it either hangs indefinitely or experiences frequent crashes that can be repeatedly triggered. This behavior constitutes a comprehensive availability attack that fundamentally undermines the database's operational integrity and service delivery capabilities. The CVSS 3.1 scoring system assigns a base score of 4.9, which reflects the moderate severity of the impact, with the availability impact component receiving the highest weight at 8.0. The attack vector requires network access and specifically targets high-privileged users, suggesting that the vulnerability may be exploited through legitimate administrative access points rather than through external network infiltration. This characteristic places the vulnerability in the context of insider threat scenarios and privilege escalation attacks.
The operational impact of CVE-2021-2387 extends far beyond simple service disruption, as database availability is critical for virtually all enterprise applications and services that rely on data persistence and retrieval. When a MySQL server experiences complete denial of service through this vulnerability, it can cascade throughout an organization's infrastructure, affecting applications that depend on database connectivity, potentially causing widespread business disruption. The vulnerability's ability to cause repeated crashes means that even if administrators attempt to recover from initial attacks, the system remains vulnerable to continuous disruption. This makes the vulnerability particularly dangerous in production environments where database uptime is essential for business operations. The attack requires only high-privileged access, which means that the vulnerability could be exploited by malicious insiders or compromised administrative accounts, creating a scenario where the threat actor already possesses legitimate access credentials. This aspect of the vulnerability aligns with the MITRE ATT&CK framework's concept of privilege escalation and persistence mechanisms, where attackers leverage existing access to cause maximum disruption.
Mitigation strategies for CVE-2021-2387 primarily focus on immediate software updates and access control measures. Organizations should prioritize updating their MySQL Server installations to versions that have addressed this vulnerability, as Oracle has released patches to resolve the issue. Additionally, implementing strict access controls and monitoring for unusual activity from high-privileged accounts can help detect potential exploitation attempts. Network segmentation and firewall rules should be reviewed to limit unnecessary access to MySQL server instances, particularly restricting access to only trusted administrative networks. The vulnerability's characteristics suggest that organizations should also implement comprehensive monitoring solutions that can detect server hangs or repeated crashes, as these may indicate exploitation attempts. Security teams should also consider implementing privileged access management solutions that can provide additional layers of control over administrative access to database systems, reducing the risk of exploitation through compromised administrative credentials.