CVE-2026-62296: HAPI FHIR: XHTML narrative parser unbounded recursion causes StackOverflow denial of service

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-07 · updated 2026-09-09
Weakness: CWE-20

Description

HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to 6.9.11, XhtmlParser.java imposes no maximum element nesting depth, so a deeply nested text.div narrative triggers unbounded recursion between parseElementInner() and parseElement(), raising a StackOverflowError. An attacker who can submit FHIR resources containing such narratives can thus crash a parsing or validation worker thread, affecting validator services and any application that parses attacker-supplied FHIR JSON or XML. This issue is fixed in version 6.9.11.

Affected products

hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.r5: before 6.9.11
hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.utilities: before 6.9.11
hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.validation: before 6.9.11
hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli: before 6.9.11
hapifhir org.hl7.fhir.core: before 6.9.11

References

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