CVE-2026-34267 Overview
A denial of service vulnerability exists in the MySQL Server product of Oracle MySQL, specifically in the Server: Optimizer component. This easily exploitable vulnerability allows a high-privileged attacker with network access via multiple protocols to compromise MySQL Server availability. Successful exploitation can result in an unauthorized ability to cause a hang or frequently repeatable crash, leading to complete denial of service of the MySQL Server.
Critical Impact
Successful exploitation enables attackers with administrative privileges to cause complete denial of service by repeatedly crashing or hanging the MySQL Server, disrupting database availability for all dependent applications.
Affected Products
- Oracle MySQL Server versions 8.0.0 through 8.0.45
Discovery Timeline
- April 21, 2026 - CVE-2026-34267 published to NVD
- April 23, 2026 - Last updated in NVD database
Technical Details for CVE-2026-34267
Vulnerability Analysis
This vulnerability is classified as CWE-400 (Uncontrolled Resource Consumption), indicating a resource exhaustion issue within the MySQL Server's Optimizer component. The flaw allows a privileged attacker to craft malicious queries or operations that consume excessive server resources, ultimately leading to a denial of service condition.
The vulnerability resides in the query optimization subsystem, which is responsible for analyzing and determining the most efficient execution plan for SQL queries. When processing specially crafted input, the optimizer can enter a state where it consumes resources without proper bounds, causing the server to hang or crash.
Root Cause
The root cause of this vulnerability is uncontrolled resource consumption within the Server: Optimizer component. The optimizer fails to properly limit resource usage when processing certain types of queries or query patterns, allowing malicious input to trigger excessive memory or CPU consumption. This lack of proper resource constraints enables an attacker to exhaust system resources and cause the database server to become unresponsive.
Attack Vector
The vulnerability is exploitable over the network through standard MySQL communication protocols. However, exploitation requires high privileges (administrative or elevated database user permissions), which limits the attack surface to authenticated users with significant database access rights.
An attacker with the necessary privileges would craft specific SQL queries or operations designed to trigger the resource exhaustion condition in the optimizer component. When the MySQL Server processes these malicious queries, the optimizer enters a pathological state, consuming excessive resources and resulting in a server hang or crash.
The attack does not require user interaction and can be executed remotely whenever the attacker has network access to the MySQL Server and possesses the required credentials.
Detection Methods for CVE-2026-34267
Indicators of Compromise
- Unexpected MySQL Server crashes or hangs, particularly during query processing
- Abnormal CPU or memory consumption by the mysqld process without corresponding workload increase
- Error logs showing optimizer-related failures or timeouts
- Repeated connection timeouts or refused connections from dependent applications
Detection Strategies
- Monitor MySQL error logs for patterns indicating optimizer crashes or abnormal terminations
- Implement query auditing to identify unusually complex or resource-intensive queries from privileged users
- Deploy behavioral analysis to detect anomalous patterns in database administrator activity
- Use SentinelOne Singularity to monitor for process crashes and resource exhaustion patterns on database servers
Monitoring Recommendations
- Configure MySQL slow query logging to capture potentially malicious queries
- Set up alerts for MySQL process crashes or unexpected restarts
- Monitor system resource utilization (CPU, memory) for database servers
- Implement connection monitoring to detect service availability degradation
How to Mitigate CVE-2026-34267
Immediate Actions Required
- Review and restrict high-privilege database accounts to only essential personnel
- Audit privileged user activity and query patterns for suspicious behavior
- Implement network segmentation to limit access to MySQL servers from untrusted networks
- Enable query logging and monitoring to detect potential exploitation attempts
Patch Information
Oracle has released security updates addressing this vulnerability as part of the April 2026 Critical Patch Update. Administrators should upgrade MySQL Server to a patched version beyond 8.0.45 as soon as possible.
For detailed patch information and download links, refer to the Oracle Security Alert April 2026.
Workarounds
- Restrict network access to MySQL Server using firewall rules to limit exposure
- Review and minimize the number of users with high-privilege database access
- Implement query timeouts and resource limits using MySQL's max_execution_time and other optimizer hints
- Consider using connection pooling with query complexity limits to prevent resource exhaustion
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
