CVE-2021-45918 in Health Care Card Web Service
Summary
by MITRE • 06/20/2022
NHI’s health insurance web service component has insufficient validation for input string length, which can result in heap-based buffer overflow attack. A remote attacker can exploit this vulnerability to flood the memory space reserved for the program, in order to terminate service without authentication, which requires a system restart to recover service.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2021-45918 affects NHI's health insurance web service component and represents a critical security flaw that stems from inadequate input validation mechanisms. This issue manifests as insufficient validation for input string length within the web service implementation, creating a pathway for malicious actors to exploit the system through heap-based buffer overflow attacks. The vulnerability resides in the application's failure to properly enforce bounds checking on user-supplied data, particularly string inputs that are processed by the health insurance web service component.
The technical exploitation of this vulnerability occurs when an attacker sends specially crafted input data that exceeds the allocated buffer size within the heap memory structure. This overflow condition allows the attacker to overwrite adjacent memory locations, potentially corrupting program execution flow and leading to denial of service conditions. The heap-based nature of the buffer overflow means that the attack specifically targets dynamically allocated memory regions, making the exploitation more complex but equally dangerous. The vulnerability does not require authentication for exploitation, which significantly increases its threat level and potential impact on service availability.
From an operational perspective, the impact of this vulnerability extends beyond simple service disruption to encompass complete system unavailability that requires manual intervention for recovery. When successfully exploited, the buffer overflow causes the memory space reserved for the program to become flooded with malicious data, resulting in program termination and service outage. The recovery process necessitates a system restart, which introduces additional operational challenges including potential data loss, extended downtime, and disruption to healthcare services that depend on the insurance web service. This type of vulnerability directly impacts the availability aspect of the CIA triad and can have serious consequences in healthcare environments where continuous service availability is critical.
The vulnerability maps to CWE-121 heap-based buffer overflow and aligns with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should implement robust input validation mechanisms that enforce strict length limits on all user-supplied data, particularly string inputs processed by web services. Mitigation strategies include implementing proper bounds checking, using safe string handling functions, and deploying input sanitization controls. Additionally, regular security testing including fuzzing and penetration testing should be conducted to identify similar vulnerabilities. The implementation of memory protection mechanisms such as stack canaries and address space layout randomization can provide additional defense-in-depth measures. Organizations should also establish incident response procedures specifically addressing service disruption events caused by buffer overflow vulnerabilities to minimize recovery time and operational impact.