CVE-2025-1000 Overview
IBM Db2 for Linux, UNIX and Windows (includes DB2 Connect Server) contains a denial of service vulnerability that could allow an authenticated user to disrupt database availability when connecting to a z/OS database. The vulnerability stems from improper handling of automatic client rerouting, which can be exploited to cause service disruption.
Critical Impact
Authenticated attackers can exploit improper client rerouting handling to cause denial of service, potentially disrupting critical database operations and business continuity.
Affected Products
- IBM Db2 for Linux 11.5.0 through 11.5.9
- IBM Db2 for UNIX 11.5.0 through 11.5.9
- IBM Db2 for Windows 11.5.0 through 11.5.9
- IBM Db2 for Linux 12.1.0 through 12.1.1
- IBM Db2 for UNIX 12.1.0 through 12.1.1
- IBM Db2 for Windows 12.1.0 through 12.1.1
- IBM DB2 Connect Server (all affected platforms and versions listed above)
Discovery Timeline
- 2025-05-05 - CVE-2025-1000 published to NVD
- 2025-11-03 - Last updated in NVD database
Technical Details for CVE-2025-1000
Vulnerability Analysis
This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The flaw exists in how IBM Db2 handles automatic client rerouting when establishing connections to z/OS databases. When an authenticated user initiates a connection that triggers the automatic client rerouting functionality, improper handling of this process can lead to resource exhaustion or service disruption.
The network-accessible nature of this vulnerability means that any authenticated user with network access to the Db2 server can potentially exploit this condition. The attack requires low complexity to execute and does not require user interaction, making it relatively straightforward for an attacker with valid credentials to exploit.
Root Cause
The root cause of CVE-2025-1000 lies in the improper resource allocation during the automatic client rerouting process. When Db2 attempts to reroute client connections to z/OS databases, the system fails to properly limit or throttle the resources consumed during this operation. This improper handling allows an authenticated attacker to trigger conditions that exhaust system resources, leading to a denial of service condition that affects the availability of the database service.
Attack Vector
The attack vector is network-based, requiring the attacker to have authenticated access to the IBM Db2 server. The exploitation scenario involves:
- An authenticated user establishes a connection to an IBM Db2 instance configured with automatic client rerouting to a z/OS database
- The attacker triggers the automatic client rerouting functionality through specific connection patterns
- Due to improper handling of resource allocation during rerouting, the system becomes overwhelmed
- The denial of service condition prevents legitimate users from accessing the database
The vulnerability specifically manifests when connecting to z/OS databases through the automatic client rerouting feature. Organizations that do not utilize z/OS database connectivity may have reduced exposure, though patching is still recommended.
Detection Methods for CVE-2025-1000
Indicators of Compromise
- Unusual patterns of connection attempts to z/OS databases from authenticated users
- Abnormal resource consumption on Db2 server instances during client rerouting operations
- Repeated connection failures or timeouts when accessing z/OS databases
- Sudden spikes in automatic client rerouting events in Db2 diagnostic logs
Detection Strategies
- Monitor Db2 diagnostic logs (db2diag.log) for excessive automatic client rerouting events or connection errors
- Implement alerting for abnormal connection patterns to z/OS databases
- Track resource utilization metrics (CPU, memory, connections) on Db2 servers and establish baseline thresholds
- Review authentication logs for suspicious user activity targeting z/OS database connections
Monitoring Recommendations
- Enable detailed logging for automatic client rerouting events in Db2 configuration
- Configure real-time alerts for resource exhaustion conditions on database servers
- Implement network monitoring to detect unusual traffic patterns to Db2 ports (typically 50000 or configured port)
- Regularly audit user permissions and connection privileges to z/OS databases
How to Mitigate CVE-2025-1000
Immediate Actions Required
- Apply the security patches provided by IBM for affected Db2 versions
- Review and restrict user access to z/OS database connections where possible
- Monitor database servers for signs of exploitation attempts
- Consider temporarily disabling automatic client rerouting if not operationally critical until patches are applied
Patch Information
IBM has released security updates to address this vulnerability. Affected organizations should apply the appropriate patches as soon as possible:
- Upgrade IBM Db2 11.5.x to a version beyond 11.5.9 that includes the security fix
- Upgrade IBM Db2 12.1.x to a version beyond 12.1.1 that includes the security fix
For detailed patch information and download instructions, refer to the IBM Support Page. Additional security context is available in the NetApp Security Advisory.
Workarounds
- Restrict authenticated access to z/OS database connections to only essential users and applications
- Implement network segmentation to limit access to Db2 servers from untrusted network segments
- Configure connection rate limiting at the network or application level if supported
- Monitor and set resource limits for Db2 instances to prevent complete service exhaustion
# Example: Review current Db2 configuration for client rerouting settings
db2 get dbm cfg | grep -i reroute
# Example: Check current connection limits
db2 get dbm cfg | grep -i max
# Example: Monitor active connections for anomalies
db2 list applications
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
