CVE-2025-53042: Oracle MySQL Server DOS Vulnerability

CVE-2025-53042 Overview

CVE-2025-53042 is a denial of service vulnerability in the Oracle MySQL Server product, specifically within the Server: Optimizer component. The flaw affects MySQL Server versions 8.0.0 through 8.0.43, 8.4.0 through 8.4.6, and 9.0.0 through 9.4.0. An authenticated attacker with high privileges and network access can exploit this vulnerability through multiple protocols to trigger a hang or repeatable crash of the MySQL Server. Oracle addressed this issue as part of the October 2025 Critical Patch Update. The vulnerability is tracked under [CWE-400: Uncontrolled Resource Consumption].

Critical Impact
Successful exploitation results in a complete denial of service of MySQL Server, halting all dependent applications and services.

Affected Products

Oracle MySQL Server versions 8.0.0 through 8.0.43
Oracle MySQL Server versions 8.4.0 through 8.4.6
Oracle MySQL Server versions 9.0.0 through 9.4.0

Discovery Timeline

2025-10-21 - CVE CVE-2025-53042 published to NVD as part of Oracle's Critical Patch Update advisory
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-53042

Vulnerability Analysis

The vulnerability resides in the MySQL Server Optimizer component, which is responsible for parsing SQL queries and generating efficient execution plans. An authenticated attacker with high database privileges can submit crafted queries that cause the optimizer to consume unbounded resources or enter an unrecoverable state. The result is a server hang or repeatable crash that produces a full denial of service.

The issue is classified under [CWE-400: Uncontrolled Resource Consumption]. Because the flaw affects availability only, confidentiality and integrity of stored data are not directly compromised. However, downtime of a database tier can cascade into application outages, transaction failures, and service-level agreement violations. The vulnerability is exploitable across multiple protocols supported by MySQL Server, including standard client connections.

Root Cause

The root cause lies in how the Optimizer handles certain query constructs or execution plans. Insufficient resource limits or missing safeguards during plan generation allow malicious inputs to exhaust CPU, memory, or trigger fatal internal states. Oracle has not published detailed technical internals; refer to the Oracle Security Advisory - CPU October 2025 for authoritative details.

Attack Vector

Exploitation requires network access to the MySQL Server and valid credentials for a high-privileged database account. The attacker submits a specially crafted query through any supported MySQL protocol. No user interaction is required. Because privileged accounts are often used by application backends, compromise of an application credential can enable this attack path against production databases.

No public proof-of-concept exploit code has been released for this vulnerability at the time of writing.

Detection Methods for CVE-2025-53042

Indicators of Compromise

Unexpected MySQL Server process crashes or restarts logged in mysqld.log or system journal
Sudden spikes in CPU or memory consumption by the mysqld process followed by service unavailability
Repeated query submissions from a single authenticated session immediately preceding server hangs
Application-tier connection timeout errors correlating with database unavailability windows

Detection Strategies

Enable MySQL general query log or slow query log to capture the SQL statements executed prior to a crash
Correlate database error logs with authentication logs to identify the account responsible for suspicious queries
Monitor for anomalous query patterns from privileged accounts, particularly complex or malformed optimizer inputs
Track MySQL Server uptime and alert on unexpected restarts that fall outside maintenance windows

Monitoring Recommendations

Deploy database activity monitoring to baseline normal query behavior and flag deviations from privileged accounts
Forward MySQL error logs and audit logs to a centralized logging platform for correlation with network and identity events
Alert on any mysqld process termination with a non-zero exit code or signal-based crash
Track connection origins for privileged accounts and alert on logins from unexpected network segments

How to Mitigate CVE-2025-53042

Immediate Actions Required

Apply the October 2025 Oracle Critical Patch Update to all affected MySQL Server instances as the primary remediation
Inventory all MySQL Server deployments and identify instances running versions 8.0.0-8.0.43, 8.4.0-8.4.6, or 9.0.0-9.4.0
Rotate credentials for any high-privileged database accounts suspected of exposure
Restrict network access to MySQL Server ports so that only trusted application hosts can connect

Patch Information

Oracle released fixes for this vulnerability in the October 2025 Critical Patch Update. Administrators should upgrade to a fixed release documented in the Oracle Security Advisory - CPU October 2025. Verify the patched version after upgrade using SELECT VERSION(); and confirm no affected build remains in production.

Workarounds

Enforce the principle of least privilege and remove unnecessary high-privileged grants from application and service accounts
Restrict MySQL Server network exposure using firewall rules, security groups, or a bastion architecture
Enable connection rate limiting and monitor for repeated crash-inducing query patterns
Configure automatic service restart with systemd to reduce downtime while remediation is planned, understanding this does not prevent exploitation

bash

# Verify installed MySQL Server version after patching
mysql -u root -p -e "SELECT VERSION();"

# Review high-privileged accounts that could exploit the flaw
mysql -u root -p -e "SELECT user, host FROM mysql.user WHERE Super_priv='Y' OR Process_priv='Y';"

# Restrict network exposure at the OS level (example: allow only application subnet)
iptables -A INPUT -p tcp --dport 3306 -s 10.0.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 3306 -j DROP