CVE-2021-2213 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 8.0.22 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-2021-2213 represents a critical availability threat within Oracle MySQL Server's optimizer component, affecting versions 8.0.22 and earlier. This issue resides 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 flaw to disrupt database operations. The attack vector operates through multiple network protocols, making the exploit surface broader and more accessible to threat actors. The CVSS score of 4.9 reflects the moderate severity impact on availability, though the potential for complete denial of service makes this vulnerability particularly concerning for production environments where database uptime is critical.
The technical flaw manifests in the optimizer's handling of specific query execution patterns that cause the MySQL Server process to enter an unstable state. When processing certain complex queries, the optimizer component fails to properly validate or handle edge cases in query planning, leading to memory corruption or execution path failures. This results in the database server either hanging indefinitely or crashing repeatedly, effectively rendering the service unavailable to legitimate users. The vulnerability's impact extends beyond simple service disruption as the repeated crashes can cause cascading failures in applications that depend on database connectivity, potentially affecting entire application stacks. The high privilege requirement for exploitation suggests that attackers must already have access to database user accounts with sufficient permissions to execute queries, though this access level is often achievable through various attack vectors including credential theft or privilege escalation.
The operational impact of CVE-2021-2213 poses significant risks to database availability and business continuity. Organizations running affected MySQL versions face potential downtime that can last from minutes to hours depending on recovery procedures and system configuration. The vulnerability's ability to cause complete denial of service means that database applications may become entirely inaccessible, affecting all dependent services and potentially leading to financial losses or compliance violations. Security teams must consider the broader implications for their incident response procedures, as the vulnerability can be exploited to create persistent availability issues that require system restarts or manual intervention to resolve. The nature of the exploit also suggests that automated monitoring systems may not immediately detect the subtle signs of a compromised optimizer, leading to delayed response times and extended service interruptions.
Organizations should prioritize immediate patching of affected MySQL Server installations to mitigate this vulnerability, as Oracle has released security updates addressing the specific optimizer flaw. The mitigation strategy should include comprehensive testing of patched versions in staging environments before production deployment to ensure compatibility with existing database workloads. Network segmentation and access controls should be reviewed to limit the attack surface, particularly ensuring that only authorized users have the necessary privileges to execute complex queries that could trigger the vulnerability. Monitoring solutions should be enhanced to detect unusual query patterns or repeated connection failures that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a variant of the broader category of software faults that can lead to denial of service attacks. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, where adversaries exploit software flaws to disrupt availability of network services. Organizations should also consider implementing database activity monitoring solutions that can detect and alert on suspicious query execution patterns that might indicate exploitation attempts against this specific vulnerability.