CVE-2026-101786 in MySQL Server
Summary
by MITRE • 10/21/2026
Vulnerability in the MySQL Server, MySQL Cluster product of Oracle MySQL (component: Server: Optimizer). Supported versions that are affected are MySQL Server: 26.7.0-26.7.1; MySQL Cluster: 26.7.0-26.7.1. Easily exploitable vulnerability allows high privileged attacker with network access via multiple protocols to compromise MySQL Server, MySQL Cluster. Successful attacks of this vulnerability can result in takeover of MySQL Server, MySQL Cluster. CVSS 3.1 Base Score 7.2 (Confidentiality, Integrity and Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).
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Analysis
by VulDB Data Team • 10/21/2026
The identified vulnerability resides within the query optimizer component of Oracle MySQL Server and MySQL Cluster versions 26.7.0 through 26.7.1, representing a critical flaw in how the database engine processes complex SQL statements. The query optimizer is responsible for determining the most efficient execution plan for retrieving or modifying data, making it a central point of control within the database architecture. A defect in this module allows an attacker with high privileges to manipulate the internal logic that selects join orders, index usage, and other optimization strategies. This flaw is particularly dangerous because it does not require user interaction or social engineering; rather, it can be triggered by submitting specifically crafted SQL queries over standard network protocols such as TCP/IP. The presence of this vulnerability indicates a breakdown in input validation or logical boundary checks within the optimizer's decision-making algorithms, allowing maliciously structured requests to exploit internal state inconsistencies or memory management errors during query execution planning.
From an operational perspective, the impact of exploiting this flaw is severe and comprehensive, encompassing confidentiality, integrity, and availability as indicated by its CVSS 3.1 base score of 7.2. A successful exploitation allows a high-privileged attacker to achieve complete takeover of the MySQL Server or Cluster instance. This level of compromise means that an adversary can read sensitive data stored in the database without authorization, alter critical records leading to data integrity loss, and potentially cause denial-of-service conditions by crashing the server process or consuming excessive resources through infinite loops triggered by malformed optimization paths. The ability to take over the service effectively grants the attacker administrative control over the underlying operating system if the MySQL service is running with elevated privileges, which is a common configuration in many enterprise environments. This aligns closely with CWE-20 Improper Input Validation and CWE-787 Out-of-bounds Write or Read, depending on whether the exploit relies on logical manipulation leading to privilege escalation or memory corruption leading to code execution.
The attack vector for this vulnerability is classified as network-accessible with low complexity, meaning that no special conditions are required beyond having valid high-level credentials and network connectivity to the database port. This classification places it within the ATT&CK framework under techniques related to Initial Access via Valid Accounts and potentially Lateral Movement if used to pivot from a compromised application server to the database layer. The requirement for high privileges suggests that this is not an unauthenticated remote code execution flaw but rather an abuse of legitimate administrative capabilities, highlighting the risk associated with over-privileged accounts in database environments. Attackers who have obtained credentials through phishing or other means can leverage these elevated permissions to execute malicious queries that trigger the optimizer bug, thereby escalating their control from a standard user role to full system dominance.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary defense is to apply the latest security patches provided by Oracle for MySQL Server and MySQL Cluster versions 26.7.0 through 26.7.1, as these updates contain code fixes that address the specific logical flaws in the optimizer module. Organizations should prioritize patching systems exposed to untrusted networks or those hosting critical data assets. In addition to patching, implementing strict principle of least privilege is essential; database administrators and application service accounts should be granted only the minimum permissions necessary for their functions, reducing the attack surface available to potential intruders who might compromise these credentials. Furthermore, deploying Web Application Firewalls (WAFs) or specialized SQL injection detection systems can help identify and block anomalous query patterns that resemble optimizer exploitation attempts before they reach the database engine. Regular auditing of user privileges and monitoring for unusual query execution times or resource spikes can also aid in early detection of such exploits in progress.