CVE-2025-2668: IBM Db2 Denial of Service Vulnerability

CVE-2025-2668 Overview

IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) versions 11.5.0 through 11.5.9 contains a denial of service vulnerability that allows an authenticated user to crash the database server by creating a specially crafted query. This vulnerability impacts the availability of critical database services and can lead to significant operational disruption.

Critical Impact

Authenticated attackers can cause complete denial of service by crashing the Db2 database server through malicious query construction, potentially disrupting business operations dependent on database availability.

Affected Products

• IBM Db2 for Linux 11.5.0 - 11.5.9
• IBM Db2 for UNIX 11.5.0 - 11.5.9
• IBM Db2 for Windows 11.5.0 - 11.5.9 (includes Db2 Connect Server)

Discovery Timeline

• 2026-01-30 - CVE-2025-2668 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2025-2668

Vulnerability Analysis

This vulnerability stems from improper handling of memory allocation when processing certain database queries. The weakness is classified under CWE-789 (Memory Allocation with Excessive Size Value) and CWE-770 (Allocation of Resources Without Limits or Throttling). When an authenticated user submits a specially crafted query to the Db2 server, the database engine fails to properly validate or limit resource allocation, leading to a server crash condition.

The attack is network-exploitable, requiring only low-privilege authentication to execute. No user interaction is required to trigger the vulnerability, and the impact is isolated to availability—there is no compromise of confidentiality or integrity. The vulnerability affects the core query processing engine of IBM Db2, making it a significant concern for organizations relying on Db2 for production database workloads.

Root Cause

The root cause of CVE-2025-2668 lies in insufficient validation of query parameters that influence memory allocation decisions within the Db2 query processor. When processing certain query structures, the server does not adequately enforce limits on resource consumption, allowing an attacker to trigger excessive memory allocation or resource exhaustion that results in a crash condition. This represents a failure in defensive programming practices around resource management in the query execution path.

Attack Vector

The attack vector for CVE-2025-2668 is network-based, requiring an attacker to have authenticated access to the Db2 database server. The attacker crafts a malicious SQL query designed to exploit the resource allocation weakness in the query processor. Upon execution of the crafted query, the server encounters an unhandled condition that leads to process termination or crash.

The vulnerability requires only standard database user privileges, making it accessible to any authenticated user with query execution rights. The attack complexity is low, requiring no special conditions or timing to exploit. Organizations with databases accessible to multiple users or applications face increased risk, as the attack could be launched by any compromised or malicious account with basic database access.

Detection Methods for CVE-2025-2668

Indicators of Compromise

• Unexpected Db2 server process terminations or crashes without clear operational cause
• Database service restarts correlating with specific user sessions or query patterns
• Error logs showing memory allocation failures or resource exhaustion conditions
• Unusual query patterns from authenticated users preceding server instability

Detection Strategies

• Monitor Db2 diagnostic logs (db2diag.log) for crash events and memory-related error codes
• Implement database activity monitoring to identify anomalous query patterns from authenticated users
• Configure alerting on Db2 service availability and unexpected restarts
• Review audit logs for queries executed immediately prior to server crash events

Monitoring Recommendations

• Enable comprehensive query logging to capture query text for forensic analysis
• Implement real-time monitoring of Db2 process health and resource consumption
• Configure automated alerts for database server crashes or unexpected terminations
• Establish baseline metrics for normal query behavior to detect anomalous activity

How to Mitigate CVE-2025-2668

Immediate Actions Required

• Apply the IBM security patch referenced in the vendor advisory as soon as possible
• Review database user privileges and restrict query execution rights to essential users only
• Implement network segmentation to limit access to Db2 servers from trusted sources
• Enable enhanced logging to capture query activity for forensic readiness

Patch Information

IBM has released a security patch addressing CVE-2025-2668. Organizations should upgrade affected Db2 installations to versions newer than 11.5.9 or apply the specific fix referenced in the IBM Support Advisory. The patch addresses the improper resource allocation handling in the query processor that enables the denial of service condition.

Workarounds

• Restrict database access to only trusted and necessary user accounts pending patch deployment
• Implement database firewall rules to filter potentially malicious query patterns if such rules can be defined
• Consider deploying Db2 in a high-availability configuration to minimize service disruption from potential crashes
• Monitor for and terminate suspicious database sessions exhibiting unusual query behavior

# Example: Review Db2 version to confirm affected status
db2level

# Example: Check diagnostic log for recent crash events
tail -500 /home/db2inst1/sqllib/db2dump/db2diag.log | grep -i "crash\|PANIC\|exception"