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CVE-2026-55471 critical CVSS 9.1

XXE (XML External Entity) in ca.uhn.hapi.fhir:org.hl7.fhir.utilities (CVE-2026-55471)

Summary

Vulnerability in ca.uhn.hapi.fhir:org.hl7.fhir.utilities (CVE-2026-55471). Confidential information can be exposed externally. Exploitable via GET /evil-fhir-xslt-ssrf.dtd. Mitigation: upgrade to 6.9.10 or later.

Original description

The description as published by the source.

Summary

org.hl7.fhir.utilities.XsltUtilities exposes two parallel families of XSLT
transform helpers. The transform(...) overloads obtain their
TransformerFactory from the project's hardened helper
XMLUtil.newXXEProtectedTransformerFactory() (which sets
ACCESS_EXTERNAL_DTD="" and ACCESS_EXTERNAL_STYLESHEET=""). The sibling
saxonTransform(...) overloads instead instantiate a bare
new net.sf.saxon.TransformerFactoryImpl() with no external-access
restriction. A document transformed through any saxonTransform(...) overload
is parsed with external general entities and external DTD/parameter entities
enabled, so an attacker who controls (or can MITM) the transformed XML obtains
XML External Entity injection: local file disclosure and blind XXE / SSRF to
arbitrary URLs reachable from the host.

XMLUtil documents that its protected factory "should be the only place where
TransformerFactory is instantiated in this project". The saxonTransform
overloads violate that contract while their same-file transform siblings
honour it.

Affected versions

org.hl7.fhir.utilities (Maven ca.uhn.hapi.fhir:org.hl7.fhir.utilities)
<= 6.9.8 (latest release at time of report; verified live on 6.9.8).
The bare net.sf.saxon.TransformerFactoryImpl() instantiation is present at
XsltUtilities.java:61, :91, and :106.

Privilege required

None at the library boundary. The exposure depends on the calling tool: any
FHIR component that runs `XsltUtilities.s…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-55471 has been found in ca.uhn.hapi.fhir:org.hl7.fhir.utilities.
Attackers can target a specific entry point like GET /evil-fhir-xslt-ssrf.dtd over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: upgrade ca.uhn.hapi.fhir:org.hl7.fhir.utilities to 6.9.10 or later.
If unsure, ask your IT team or search "ca.uhn.hapi.fhir:org.hl7.fhir.utilities CVE-2026-55471" on the vendor's site.

CVE-2026-55471 (ca.uhn.hapi.fhir:org.hl7.fhir.utilities) — CWE-611 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /evil-fhir-xslt-ssrf.dtd / org.hl7.fhir.utilities.XsltUtilities / TransformerFactory / XMLUtil
Patched: 6.9.10 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-611) exists in ca.uhn.hapi.fhir:org.hl7.fhir.utilities. Attackers reach the vulnerable code path via GET /evil-fhir-xslt-ssrf.dtd without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of ca.uhn.hapi.fhir:org.hl7.fhir.utilities. Attack surface: GET /evil-fhir-xslt-ssrf.dtd / org.hl7.fhir.utilities.XsltUtilities / TransformerFactory / XMLUtil.

🔥 Severity

Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 6.9.10.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual GET /evil-fhir-xslt-ssrf.dtd requests with malformed payloads or SQL meta-characters. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで ca.uhn.hapi.fhir:org.hl7.fhir.utilities を使っているサービスとバージョンを洗い出す。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'GET /evil-fhir-xslt-ssrf.dtd' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで GET /evil-fhir-xslt-ssrf.dtd への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade ca.uhn.hapi.fhir:org.hl7.fhir.utilities to 6.9.10

    ステージング環境で 6.9.10 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against GET /evil-fhir-xslt-ssrf.dtd on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

maven ca.uhn.hapi.fhir:org.hl7.fhir.utilities
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.9.10"}]}]

References

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