CVE-2025-1991 Overview
CVE-2025-1991 is a high-severity integer underflow vulnerability affecting IBM Informix Dynamic Server versions 12.10, 14.10, and 15.0. This vulnerability allows a remote attacker to cause a denial of service condition by sending specially crafted network packets that trigger an integer underflow during packet processing.
Critical Impact
Remote attackers can exploit this integer underflow vulnerability to disrupt database services without authentication, potentially causing significant business impact through service unavailability.
Affected Products
- IBM Informix Dynamic Server 12.10
- IBM Informix Dynamic Server 14.10
- IBM Informix Dynamic Server 15.0
Discovery Timeline
- 2025-06-28 - CVE-2025-1991 published to NVD
- 2025-08-14 - Last updated in NVD database
Technical Details for CVE-2025-1991
Vulnerability Analysis
This vulnerability is classified under CWE-191 (Integer Underflow), which occurs when a mathematical operation results in a value smaller than the minimum value that can be stored in the allocated memory space. In the context of IBM Informix Dynamic Server, this integer underflow manifests during the processing of network packets received by the database server.
When the server receives maliciously crafted packets, the integer underflow can cause unexpected behavior in memory allocation or buffer operations, leading to service disruption. The network-accessible nature of this vulnerability means that attackers do not require any privileges or user interaction to trigger the denial of service condition.
Root Cause
The root cause lies in improper handling of integer arithmetic operations within IBM Informix Dynamic Server's packet processing logic. When processing certain packet fields, the server performs calculations that can result in integer underflow if the input values are not properly validated. This causes the resulting value to wrap around to an unexpectedly large positive number, which can lead to incorrect memory operations and subsequent service crashes.
Attack Vector
This vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can send specially crafted packets to the Informix Dynamic Server that contain values designed to trigger the integer underflow condition during processing.
The attack workflow involves:
- Identifying a target IBM Informix Dynamic Server instance accessible over the network
- Crafting malicious packets containing values that will cause an integer underflow during arithmetic operations
- Sending the crafted packets to the server's listening port
- The server processes the packets, triggering the integer underflow
- The resulting miscalculation causes service disruption or crash
No proof-of-concept code is publicly available for this vulnerability. The technical details involve the manipulation of packet field values that, when processed by the server's internal arithmetic operations, produce an underflow condition leading to denial of service.
Detection Methods for CVE-2025-1991
Indicators of Compromise
- Unexpected IBM Informix Dynamic Server service crashes or restarts
- Anomalous network traffic patterns targeting Informix server ports
- Log entries indicating memory-related errors or unexpected service terminations
- Increased connection attempts from suspicious or unknown IP addresses
Detection Strategies
- Monitor network traffic for malformed or unusually structured packets destined for Informix server ports
- Implement intrusion detection rules to identify packets with suspicious field values that could trigger integer underflow
- Enable comprehensive logging on IBM Informix Dynamic Server instances to capture crash events and error conditions
- Deploy network-based anomaly detection to identify unusual traffic patterns targeting database services
Monitoring Recommendations
- Configure alerting for IBM Informix Dynamic Server service availability and unexpected restarts
- Implement real-time monitoring of server resource utilization for signs of denial of service attacks
- Establish baseline network traffic patterns to detect anomalous connection attempts
- Review server logs regularly for crash events correlated with specific network activity
How to Mitigate CVE-2025-1991
Immediate Actions Required
- Apply the security patch from IBM as soon as possible for all affected Informix Dynamic Server versions
- Implement network segmentation to limit exposure of IBM Informix Dynamic Server instances
- Configure firewall rules to restrict access to Informix server ports from trusted sources only
- Enable enhanced logging to capture potential exploitation attempts
Patch Information
IBM has released a security advisory addressing this vulnerability. Administrators should consult the IBM Support Article for detailed patch information and download links for the affected versions (12.10, 14.10, and 15.0).
Workarounds
- Restrict network access to IBM Informix Dynamic Server instances using firewall rules to allow connections only from trusted IP addresses
- Deploy a web application firewall or network intrusion prevention system capable of inspecting and filtering malicious packets
- Consider placing Informix servers behind a reverse proxy or load balancer that can provide additional packet inspection
- Implement rate limiting on connections to Informix server ports to reduce the impact of potential exploitation attempts
# Example firewall configuration to restrict Informix access
# Restrict access to Informix default port (example using iptables)
iptables -A INPUT -p tcp --dport 9088 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 9088 -j DROP
# For custom Informix port, replace 9088 with your configured port
# Ensure to save rules for persistence
iptables-save > /etc/iptables/rules.v4
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
