CVE-2025-36427: IBM Db2 Denial of Service Vulnerability

CVE-2025-36427 Overview

IBM Db2 for Linux, UNIX and Windows (includes Db2 Connect Server) contains a vulnerability that could allow an authenticated user to cause a denial of service condition. The vulnerability stems from insufficient validation of special elements in data query logic, which can be exploited to disrupt database availability.

Critical Impact
Authenticated attackers can exploit improper input validation in query processing to cause service disruption, potentially impacting business-critical database operations and application availability.

Affected Products

IBM Db2 for Linux
IBM Db2 for UNIX
IBM Db2 for Windows (includes Db2 Connect Server)

Discovery Timeline

2026-01-30 - CVE CVE-2025-36427 published to NVD
2026-02-04 - Last updated in NVD database

Technical Details for CVE-2025-36427

Vulnerability Analysis

This vulnerability is classified under CWE-1284 (Improper Validation of Specified Quantity in Input), indicating that IBM Db2 fails to properly validate certain special elements within data query logic before processing. The flaw requires network access and low-privilege authentication to exploit, making it accessible to any authenticated database user.

The vulnerability allows an attacker to craft malicious queries containing specially formatted elements that bypass validation checks. When processed by the database engine, these queries can trigger resource exhaustion or processing failures that result in service unavailability. While the attack does not compromise data confidentiality or integrity, the impact on availability is significant for organizations relying on Db2 for critical operations.

Root Cause

The root cause lies in insufficient validation of special elements within the data query parsing logic. IBM Db2's query processor does not adequately sanitize or validate certain input patterns before executing queries. This improper validation allows crafted queries to trigger unexpected behavior in the database engine, leading to denial of service conditions. The weakness relates to CWE-1284, where the software receives input specifying a quantity but fails to validate that the quantity has expected properties.

Attack Vector

The attack is network-based and requires low-privilege authentication to the Db2 database. An attacker with valid database credentials can submit specially crafted queries through standard database connection interfaces. The exploitation does not require user interaction and can be performed remotely. The attacker leverages the query submission mechanism to send malformed data query logic that exploits the validation gap, causing the database service to become unavailable.

The attack flow involves:

Establishing an authenticated connection to the IBM Db2 instance
Crafting a query containing specially formatted elements that exploit the validation weakness
Submitting the malicious query through the database interface
The query processor fails to properly validate the special elements, leading to service disruption

Detection Methods for CVE-2025-36427

Indicators of Compromise

Unexpected database service crashes or restarts without apparent cause
Anomalous query patterns from authenticated users with unusual special characters or formatting
Database error logs showing validation failures or parsing exceptions in query processing
Performance degradation followed by service unavailability

Detection Strategies

Monitor Db2 diagnostic logs for repeated query parsing errors or validation exceptions
Implement database activity monitoring to flag queries with unusual structures or special element patterns
Configure alerts for abnormal database service restarts or availability issues
Review authentication logs for suspicious user activity preceding service disruptions

Monitoring Recommendations

Enable detailed query logging to capture malformed query attempts
Set up real-time alerting on Db2 service health metrics and availability status
Implement user behavior analytics to identify anomalous query submission patterns
Monitor system resource utilization for signs of resource exhaustion attacks

How to Mitigate CVE-2025-36427

Immediate Actions Required

Apply the security patch from IBM as soon as possible by visiting the IBM Support Page
Review and restrict database user privileges to minimize the attack surface
Implement network segmentation to limit database access to authorized systems only
Audit current database users and remove unnecessary accounts

Patch Information

IBM has released a security update to address this vulnerability. Administrators should review the official IBM security bulletin available at the IBM Support Page for specific patch details, affected versions, and installation instructions. The patch addresses the insufficient validation of special elements in data query logic.

Workarounds

Restrict database access to only trusted and necessary users until patches can be applied
Implement database firewalls or query filtering solutions to detect and block potentially malicious query patterns
Enable enhanced auditing to monitor all query activity from authenticated users
Consider temporarily limiting query capabilities for non-essential users during the patching window

bash

# Example: Restrict database connections to specific IP ranges (consult IBM documentation for your environment)
# Review db2 configuration for connection restrictions
db2 get dbm cfg | grep -i "svcename\|comm"

# Enable audit logging for query monitoring
db2audit configure scope all status both
db2audit start