CVE-2026-55471 in HAPI FHIR
Summary
by MITRE • 07/09/2026
HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.10, org.hl7.fhir.utilities.XsltUtilities saxonTransform(...) overloads instantiated a bare net.sf.saxon.TransformerFactoryImpl() without ACCESS_EXTERNAL_DTD or ACCESS_EXTERNAL_STYLESHEET restrictions, allowing an attacker who controls or can tamper with transformed XML to trigger XML External Entity injection for local file disclosure and blind XXE or SSRF to arbitrary URLs reachable from the host. This issue is fixed in version 6.9.10.
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Analysis
by VulDB Data Team • 07/09/2026
The HAPI FHIR library represents a comprehensive Java implementation of the HL7 FHIR standard designed to facilitate healthcare data interoperability across different systems. This widely adopted framework enables organizations to exchange clinical information using standardized formats while maintaining compliance with healthcare industry requirements. The vulnerability discovered in versions prior to 6.9.10 specifically targets the XsltUtilities class within the org.hl7.fhir.utilities package, which handles XML transformation operations for FHIR data processing.
The technical flaw resides in how the saxonTransform(...) method instantiates a TransformerFactoryImpl without implementing proper security restrictions. This implementation fails to configure essential Saxon transformer properties including ACCESS_EXTERNAL_DTD and ACCESS_EXTERNAL_STYLESHEET, which are critical controls that prevent external entity resolution during XML processing. When attackers can manipulate or control the XML content being transformed, they gain the ability to exploit XML External Entity vulnerabilities through carefully crafted payloads.
The operational impact of this vulnerability extends beyond simple local file disclosure capabilities. Attackers with the ability to influence XML transformation processes can execute blind XXE attacks that may lead to unauthorized data access, server-side request forgery against internal network resources, or even enable further exploitation chains. The vulnerability particularly affects environments where FHIR data processing occurs with untrusted input sources, making it a significant concern for healthcare organizations handling sensitive patient information. This issue aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and represents a classic server-side request forgery vector through XML parsing mechanisms.
The security implications of this vulnerability are particularly severe in healthcare environments where compliance with regulations such as HIPAA requires stringent controls over data access and processing. The attack surface expands when considering that FHIR implementations often process data from multiple sources including external systems, mobile applications, or patient portals where input validation may be insufficient. Organizations using vulnerable versions face potential exposure to unauthorized data retrieval, internal network reconnaissance, and service disruption through SSRF attacks targeting internal services. Remediation requires updating to version 6.9.10 or later, which properly implements the necessary Saxon security restrictions. Additionally, organizations should implement input validation controls, monitor XML processing activities, and consider network segmentation to limit potential attack vectors. This vulnerability demonstrates the critical importance of maintaining proper XML parser configurations in healthcare interoperability frameworks where data integrity and confidentiality are paramount considerations.
The fix implemented in version 6.9.10 addresses the root cause by properly configuring the Saxon TransformerFactory with appropriate restrictions on external entity resolution, thereby preventing attackers from exploiting XXE vulnerabilities through the XML transformation pathways. This represents a fundamental security improvement that aligns with industry best practices for secure XML processing and helps organizations maintain compliance with healthcare security standards while reducing their attack surface against common web application vulnerabilities.