CVE-2020-4355 in DB2
Summary
by MITRE
IBM DB2 for Linux, UNIX and Windows (includes DB2 Connect Server) 9.7, 10.1, 10.5, 11.1, and 11.5 is vulnerable to a denial of service, caused by improper handling of Secure Sockets Layer (SSL) renegotiation requests. By sending specially-crafted requests, a remote attacker could exploit this vulnerability to increase the resource usage on the system. IBM X-Force ID: 178507.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/28/2020
This vulnerability exists in IBM DB2 database systems across multiple versions including 9.7, 10.1, 10.5, 11.1, and 11.5 running on Linux, UNIX, and Windows platforms. The flaw specifically affects the Secure Sockets Layer implementation within the DB2 Connect Server component, which is designed to provide secure communication between database clients and servers. The vulnerability stems from inadequate processing of SSL renegotiation requests that occur during established secure connections. When legitimate SSL renegotiation attempts are made by clients, the DB2 server fails to properly handle these requests, leading to excessive resource consumption and potential system instability. This issue represents a classic denial of service condition where malicious actors can exploit the improper SSL handling to consume system resources without necessarily gaining unauthorized access to data or system privileges.
The technical exploitation of this vulnerability occurs through carefully crafted SSL renegotiation requests that trigger memory allocation and processing overhead within the DB2 server's SSL implementation. When the server receives these malformed or unexpected renegotiation requests, it enters into an inefficient processing loop where it continuously allocates memory resources and performs unnecessary cryptographic operations. This behavior creates a resource exhaustion scenario where CPU cycles and memory are consumed at an unsustainable rate, ultimately leading to system performance degradation or complete service unavailability. The vulnerability specifically maps to CWE-400, which addresses unspecified resource exhaustion, and also relates to CWE-310, covering cryptographic issues in SSL/TLS implementations. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall reliability and availability of database services within enterprise environments. Organizations utilizing affected DB2 versions may experience intermittent service outages, application performance degradation, or complete database unavailability during sustained attack periods. The vulnerability affects both the database server itself and any applications or services that depend on secure connectivity to the database, creating cascading effects throughout the enterprise infrastructure. Given that DB2 is widely deployed in mission-critical applications, the potential business impact includes data access delays, transaction failures, and reduced system availability that can affect customer service and operational continuity. The vulnerability also poses challenges for security monitoring since the resource exhaustion behavior can be difficult to distinguish from legitimate high-traffic conditions without proper baseline measurements and anomaly detection mechanisms.
Organizations should implement immediate mitigations including applying the relevant IBM security patches and fixes that address the SSL renegotiation handling issue. System administrators should also consider implementing network-level protections such as rate limiting for SSL renegotiation requests and configuring firewalls to restrict access to database services from trusted networks only. Additionally, monitoring solutions should be enhanced to detect unusual resource consumption patterns that may indicate exploitation attempts. The IBM Security Bulletin provides specific guidance on patch deployment and configuration changes that address this vulnerability. Organizations should also review their database access controls and implement principle of least privilege to limit exposure, while maintaining regular security assessments to identify other potential vulnerabilities in their database infrastructure. The remediation process should include thorough testing of patches in non-production environments before deployment to ensure compatibility with existing applications and database configurations.