CVE-2026-45367 in HAPI FHIR
Summary
by MITRE • 07/16/2026
HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.7, the FHIRPathEngine implementation passes user-controlled regular expressions from matches(), matchesFull(), and replaceMatches() to Java regex operations without effective timeouts, allowing catastrophic backtracking and denial of service. This issue is fixed in version 6.9.7.
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Analysis
by VulDB Data Team • 07/16/2026
The HAPI FHIR library represents a comprehensive Java implementation of the HL7 FHIR standard, which serves as the foundation for healthcare data exchange and interoperability across clinical systems. This widely adopted framework enables seamless communication between diverse healthcare applications by providing standardized formats for representing clinical information. The FHIRPathEngine component within this ecosystem specifically implements the FHIRPath query language, which allows developers to navigate and extract data from FHIR resources using path expressions similar to XPath. The vulnerability affects versions prior to 6.9.7 where the implementation fails to properly handle user-supplied regular expressions in core string manipulation functions.
The technical flaw manifests in the FHIRPathEngine's handling of three critical methods: matches(), matchesFull(), and replaceMatches(). These functions accept user-controlled regular expressions as input parameters and directly pass them to underlying Java regex operations without implementing proper timeout mechanisms. This design oversight creates a vulnerability that can be exploited through catastrophic backtracking attacks, where maliciously crafted regular expressions cause the regex engine to consume excessive computational resources. The absence of timeout controls allows these operations to potentially run indefinitely or for extended periods, consuming system resources and preventing legitimate processing.
The operational impact of this vulnerability extends beyond simple performance degradation into full denial of service conditions that can compromise entire healthcare systems. When exploited, attackers can craft regular expressions that trigger exponential backtracking behavior in the Java regex engine, causing CPU utilization to spike dramatically and potentially leading to complete system unresponsiveness. This risk is particularly severe in healthcare environments where system availability is critical for patient care delivery, as such an attack could prevent access to vital medical records, diagnostic information, and treatment protocols. The vulnerability affects any application using HAPI FHIR versions prior to 6.9.7 that processes user input through these specific string manipulation functions.
Security practitioners should prioritize upgrading to version 6.9.7 or later to address this vulnerability, as it represents a critical denial of service risk in healthcare interoperability systems. The fix implemented in version 6.9.7 likely includes the introduction of proper timeout mechanisms for regex operations, preventing unlimited execution time for user-controlled patterns. Organizations should also implement input validation measures and consider additional monitoring for unusual regex pattern usage that might indicate attempted exploitation. This vulnerability aligns with CWE-400, which categorizes improper resource management in the context of regular expression processing, and maps to ATT&CK technique T1499.004 for denial of service through resource exhaustion attacks. The remediation process should include comprehensive testing of all FHIRPath operations that utilize user input to ensure the timeout mechanisms function correctly and do not inadvertently affect legitimate use cases.
The broader implications of this vulnerability highlight the importance of secure coding practices in healthcare software development, where the stakes are particularly high due to the critical nature of medical information systems. Healthcare organizations should conduct thorough vulnerability assessments across their FHIR-based applications and implement proper security controls to prevent similar issues in other components that may process user-supplied patterns or regular expressions. This incident underscores the necessity of applying defense-in-depth strategies, including input sanitization, timeout enforcement, and resource monitoring, particularly in systems handling sensitive healthcare data where availability and reliability are paramount for patient safety and care delivery.