CVE-2021-2171 in MySQL Server
Summary
by MITRE • 04/23/2021
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Replication). Supported versions that are affected are 5.7.33 and prior and 8.0.23 and prior. Difficult to exploit 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 4.4 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:H/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-2021-2171 affects the MySQL Server replication component and represents a significant availability risk for database systems. This flaw exists within Oracle MySQL versions 5.7.33 and earlier, as well as 8.0.23 and prior, indicating it spans multiple major versions and has been present for considerable time. The vulnerability is classified as difficult to exploit, requiring an attacker with high privileges and network access through multiple protocols, yet its potential impact remains severe enough to warrant immediate attention from security professionals. The CVSS 3.1 score of 4.4 reflects the availability impact, with a vector indicating network access, high attack complexity, high privileges required, and no user interaction needed, suggesting that the attack surface is limited but the consequences are substantial.
The technical nature of this vulnerability involves a flaw in the server replication functionality that can be triggered by a specially crafted sequence of replication operations. When successfully exploited, the vulnerability allows an attacker to cause the MySQL Server to hang or experience frequently repeatable crashes, effectively resulting in a complete denial of service condition. This type of vulnerability falls under CWE-121, which deals with stack-based buffer overflow conditions, or more broadly CWE-400, which covers resource exhaustion vulnerabilities that can lead to denial of service scenarios. The replication component is particularly susceptible because it handles complex data synchronization processes that must maintain strict consistency and reliability, making any instability in this area potentially catastrophic for database operations.
The operational impact of this vulnerability extends far beyond simple service disruption, as MySQL servers often serve as critical infrastructure components for enterprise applications, web services, and data-driven systems. When a MySQL server becomes unavailable due to this vulnerability, it can cause cascading failures throughout dependent applications and services, potentially affecting business operations, customer access, and data integrity. The requirement for high privileged access and network connectivity means that the attack vector is somewhat limited, but organizations with compromised accounts or those that fail to properly segment their network access may find themselves vulnerable. This aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation, as the vulnerability requires elevated privileges to exploit effectively, making it a potential vector for insider threats or compromised administrative accounts.
Organizations should implement immediate mitigations including applying the relevant Oracle security patches, which would address the root cause of the replication flaw. Network segmentation and access controls should be reviewed to ensure that only authorized personnel have the necessary privileges to perform replication operations, aligning with the principle of least privilege and reducing the attack surface. Monitoring and logging of replication activities should be enhanced to detect anomalous patterns that might indicate exploitation attempts. Additionally, implementing intrusion detection systems that can identify unusual crash patterns or replication protocol anomalies would provide early warning capabilities. Regular security assessments and vulnerability scanning should include checks for this specific vulnerability, particularly in environments where MySQL servers handle critical business data. The remediation process should also involve comprehensive testing of patches in non-production environments before deployment to ensure that the fixes do not introduce compatibility issues with existing database operations or application integrations.