FHIR Validator: Unauthenticated Blind SSRF via /loadIG Endpoint Enables Internal Network Probing

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

EPSS

• CVE-2026-34360: 0.24% estimated exploitation activity in the next 30 days; percentile 15.73 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The /loadIG HTTP endpoint in the FHIR Validator HTTP service accepts a user-supplied URL via JSON body and makes server-side HTTP requests to it without any hostname, scheme, or domain validation. An unauthenticated attacker with network access to the validator can probe internal network services, cloud metadata endpoints, and map network topology through error-based information leakage. With explore=true (the default for this code path), each request triggers multiple outbound HTTP calls, amplifying reconnaissance capability. Details Root cause chain: 1. LoadIGHTTPHandler.handle() reads the ig field from user-supplied JSON and passes it directly to IgLoader.loadIg() with no validation: 2. loadIg() calls loadIgSource(srcPackage, recursive, true) with explore=true (IgLoader.java:153). 3. loadIgSource() checks Common.isNetworkPath(src) which only verifies the URL starts with http: or https: — no host/IP validation (Common.java:14-16). 4. The URL reaches ManagedWebAccess.get()…

Published by the source

30 Mar 2026, 17:21 UTC

Last modified by the source

31 Mar 2026, 18:55 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3ww8-jw56-9f5h

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# Patch Next advisory brief: CVE-2026-34360

Advisory: FHIR Validator: Unauthenticated Blind SSRF via /loadIG Endpoint Enables Internal Network Probing
IDs: CVE-2026-34360, GHSA-3ww8-jw56-9f5h
Record: https://patchnext.com/advisories/cve-2026-34360 (revision 1, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ca.uhn.hapi.fhir:org.hl7.fhir.core 6.9.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven ca.uhn.hapi.fhir:org.hl7.fhir.core: affected < 6.9.4; fixed in 6.9.4

## Suggested inspection (read-only)
- Maven ca.uhn.hapi.fhir:org.hl7.fhir.core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ca.uhn.hapi.fhir:org.hl7.fhir.core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3ww8-jw56-9f5h (GitHub-reviewed advisory GHSA-3ww8-jw56-9f5h lists affected ranges: Maven ca.uhn.hapi.fhir:org.hl7.fhir.core >=0 <6.9.4)

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