CVE-2026-55471: HAPI FHIR: XXE in XsltUtilities.saxonTransform via unhardened Saxon TransformerFactory

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-07-08 · updated 2026-10-25
Weakness: CWE-611

Description

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.

Affected products

hapifhir org.hl7.fhir.core: before 6.9.10 — fixed in 6.9.10

How to fix

Upgrade to a fixed version: hapifhir org.hl7.fhir.core 6.9.10. Check the vendor advisory for mitigations.

References

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