---
title: "CVE-2026-55471: HAPI FHIR: XXE in XsltUtilities.saxonTransform via unhardened Saxon TransformerFactory"
url: https://erroneo.us/security/cve/CVE-2026-55471/
description: "CVE-2026-55471 (ca.uhn.hapi.fhir:org.hl7.fhir.utilities (Maven)): HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-08
date_modified: 2026-07-09
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-55471"
kev: false
cvss: 8.7
epss: 0.00569
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Normal patch cycle. No exploitation signal; fix it in your next routine update if you are affected. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.6% , percentile 46: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 46% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes ca.uhn.hapi.fhir:org.hl7.fhir.utilities (Maven) <= 6.9.9, fixed in 6.9.10 . Check your lockfile, including transitive dependencies.

## What it is

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 ACCESSEXTERNALDTD or ACCESSEXTERNALSTYLESHEET 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 packages

- Maven `ca.uhn.hapi.fhir:org.hl7.fhir.utilities` <= 6.9.9 → fixed: 6.9.10

## Affected products (CVE record)

- hapifhir org.hl7.fhir.core: < 6.9.10

## Severity

- GitHub_M CVSS 4.0: 8.7 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:L/SI:N/SA:N`
- GitHub CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable yes , technical impact partial .
- FIRST EPSS (model of 2026-10-21): 0.57% probability of exploitation activity in the next 30 days; percentile 46.

## Sources

- [GitHub Advisory GHSA-2f55-g35j-5jmf](https://github.com/advisories/GHSA-2f55-g35j-5jmf)
- [CVE.org record CVE-2026-55471](https://www.cve.org/CVERecord?id=CVE-2026-55471)
- [NVD entry CVE-2026-55471](https://nvd.nist.gov/vuln/detail/CVE-2026-55471)
- [github.com](https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-2f55-g35j-5jmf)
- [github.com](https://github.com/hapifhir/org.hl7.fhir.core/commit/01ca2ecdefec9b33204d2495fe78af8c0dc52298)
- [github.com](https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.10)

---
Source page: https://erroneo.us/security/cve/CVE-2026-55471/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt