CVE-2026-62296 HAPI FHIR: XHTML narrative parser unbounded recursion causes StackOverflow denial of service
An attacker can crash HAPI FHIR parser threads by submitting deeply nested XHTML narratives, causing a denial of service in applications processing FHIR data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-62296?
CVE-2026-62296 is a high-severity denial of service vulnerability in hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.r5, published on 7 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-62296?
How do I fix CVE-2026-62296?
No fix has been published for CVE-2026-62296 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-62296 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62296 exists.
Sources
Also known as GHSA-5v24-q6x8-hc38.