CVE-2025-36123 Overview
IBM Db2 for Linux, UNIX and Windows (includes DB2 Connect Server) contains a resource exhaustion vulnerability that could allow a local authenticated user to cause a denial of service condition. The vulnerability is triggered when copying large tables containing XML data, due to improper allocation of system resources (CWE-770: Allocation of Resources Without Limits or Throttling).
Critical Impact
Local users with database access can exhaust system resources by performing copy operations on large XML-containing tables, leading to database unavailability.
Affected Products
- IBM Db2 for Linux, UNIX and Windows 11.5.0 - 11.5.9
- IBM Db2 for Linux, UNIX and Windows 12.1.0 - 12.1.3
- IBM DB2 Connect Server (all affected versions above)
Discovery Timeline
- 2026-01-30 - CVE-2025-36123 published to NVD
- 2026-02-05 - Last updated in NVD database
Technical Details for CVE-2025-36123
Vulnerability Analysis
This vulnerability represents a resource exhaustion flaw in IBM Db2's handling of XML data during table copy operations. The underlying issue stems from CWE-770: Allocation of Resources Without Limits or Throttling, where the database engine fails to properly manage memory allocation when processing large volumes of XML content.
When a local user initiates a copy operation on a table containing substantial XML data, the Db2 engine allocates system resources without adequate bounds checking or throttling mechanisms. This can lead to excessive memory consumption, potentially exhausting available system resources and causing the database service to become unresponsive or crash entirely.
The vulnerability requires local access and a low-privilege authenticated session, meaning an attacker would need valid credentials to the database system. While this limits the attack surface compared to remotely exploitable vulnerabilities, it poses significant risk in multi-tenant database environments or systems where multiple users have database access.
Root Cause
The root cause is improper resource allocation handling within the Db2 engine when processing XML data structures during copy operations. The system fails to implement proper limits on memory allocation, allowing unbounded resource consumption when handling large XML datasets. This represents a classic resource exhaustion pattern where input size is not adequately validated against available system resources before allocation occurs.
Attack Vector
The attack vector is local, requiring an authenticated user with permissions to perform table copy operations. The attacker must identify or create a table containing significant XML data and then initiate a copy operation that triggers the improper resource allocation. The attack requires no user interaction beyond the attacker's own actions and directly impacts system availability.
The exploitation scenario involves a malicious insider or compromised account with database access privileges sufficient to execute copy commands on XML-containing tables. By targeting tables with large XML columns or creating specially crafted tables with excessive XML content, the attacker can force the database engine to consume all available memory.
Detection Methods for CVE-2025-36123
Indicators of Compromise
- Unusual memory consumption spikes during database copy operations
- Db2 process (db2sysc) consuming abnormally high amounts of system memory
- Database service becoming unresponsive during XML table operations
- System logs showing out-of-memory errors related to Db2 processes
Detection Strategies
- Monitor Db2 database logs for copy operations involving large XML tables
- Implement resource monitoring on database servers to detect abnormal memory allocation patterns
- Configure alerting thresholds for Db2 process memory consumption
- Audit user activities involving bulk copy operations on tables with XML columns
Monitoring Recommendations
- Enable detailed logging for copy and export operations within Db2
- Deploy system-level monitoring for memory utilization on database hosts
- Implement database activity monitoring to track operations on XML-heavy tables
- Set up automated alerts when Db2 memory consumption exceeds defined thresholds
How to Mitigate CVE-2025-36123
Immediate Actions Required
- Review the IBM Security Advisory for official patch information
- Restrict copy operation privileges to trusted database administrators only
- Implement resource limits for database operations where possible
- Monitor systems for signs of exploitation while awaiting patch deployment
Patch Information
IBM has released security updates addressing this vulnerability. Organizations running affected versions of IBM Db2 (11.5.0 - 11.5.9 and 12.1.0 - 12.1.3) should consult the IBM Support Page for detailed patching instructions and to obtain the appropriate fix packs for their environment.
Workarounds
- Restrict database user privileges to limit who can perform copy operations on XML tables
- Implement operating system-level resource limits (ulimits) for the Db2 service account
- Consider temporarily disabling access to tables with large XML content for non-essential users
- Deploy additional monitoring to detect and respond to resource exhaustion attempts
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
