Vulnerability · Published Aug 7, 2026 · Assigned by GitHub_M
CVE-2026-62296HAPI FHIR: XHTML narrative parser unbounded recursion causes StackOverflow denial of service
High 7.5
In plain English
A high-severity improper input validation in ca.uhn.hapi.fhir:org.hl7.fhir.r5 from hapifhir. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities).
Official 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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| hapifhir | org.hl7.fhir.core | < 6.9.11 |
| hapifhir | ca.uhn.hapi.fhir:org.hl7.fhir.r5 | < 6.9.11 |
| hapifhir | ca.uhn.hapi.fhir:org.hl7.fhir.utilities | < 6.9.11 |
| hapifhir | ca.uhn.hapi.fhir:org.hl7.fhir.validation | < 6.9.11 |
| hapifhir | ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli | < 6.9.11 |
Weakness: CWE-20, CWE-400, CWE-674 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H