CVE-2021-35546 in MySQL Server
Summary
by MITRE • 10/20/2021
Vulnerability in the MySQL Server product of Oracle MySQL (component: Server: Replication). Supported versions that are affected are 8.0.26 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 • 05/17/2025
The vulnerability identified as CVE-2021-35546 represents a significant availability threat within Oracle MySQL Server's replication functionality. This flaw exists in the Server: Replication component of MySQL versions 8.0.26 and earlier, making it a critical concern for database administrators managing high-traffic environments where replication stability is paramount. The vulnerability's classification as easily exploitable indicates that attackers with high privileges and network access can leverage this weakness without requiring specialized tools or extensive technical knowledge, posing a substantial risk to database availability.
The technical nature of this vulnerability stems from improper handling of replication operations that can lead to system instability. When exploited, the flaw enables attackers to cause complete denial of service conditions by inducing hangs or frequent crashes in the MySQL Server process. This occurs through manipulation of replication protocols that are typically used for data synchronization between master and slave servers. The vulnerability specifically targets the replication subsystem where data consistency and server stability are maintained, making it particularly dangerous in production environments where replication is actively used for backup, failover, or load distribution purposes.
From an operational perspective, the impact of this vulnerability extends beyond simple service interruption to potentially compromise entire database infrastructures. The CVSS 3.1 score of 4.9 indicates a moderate to high severity level, with the availability impact rating of high (A:H) reflecting the complete denial of service potential. Attackers with network access and high privileges can repeatedly trigger the crash conditions, potentially leading to sustained service disruption that could affect business operations, data availability, and overall system reliability. Organizations relying on MySQL replication for critical data operations face significant risk of operational downtime and potential data loss during attack scenarios.
Security professionals should note that this vulnerability aligns with CWE-119, which addresses improper restriction of operations within a limited scope, and maps to ATT&CK technique T1499.004 for endpoint denial of service attacks. The attack vector requires network access and high privilege levels, suggesting that this vulnerability may be exploited through compromised administrative accounts or network infiltration. Organizations should implement immediate mitigations including applying the latest MySQL patches, implementing network segmentation to limit access to replication ports, and monitoring for unusual replication activity patterns that could indicate exploitation attempts.
The recommended remediation approach involves upgrading to MySQL Server version 8.0.27 or later, which contains the necessary patches to address this replication instability issue. Additionally, organizations should review their network access controls to ensure that replication protocols are not exposed to untrusted networks, and consider implementing intrusion detection systems to monitor for potential exploitation attempts. Regular security assessments of replication configurations should be conducted to identify and remediate any misconfigurations that could exacerbate the vulnerability's impact. Organizations should also maintain comprehensive backup and disaster recovery procedures to minimize the operational impact should exploitation occur despite preventive measures.