CVE-2026-55470 HAPI FHIR: DSTU2 FHIRPathEngine.matches() missing RegexTimeout protection allows ReDoS
An unauthenticated attacker can cause server CPU exhaustion via catastrophic regex backtracking in the HAPI FHIR DSTU2 module.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55470?
CVE-2026-55470 is a high-severity denial of service vulnerability in hapifhir org.hl7.fhir.core, published on 8 Jul 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 6.9.10, the fix for CVE-2026-45367 incompletely patched the DSTU2 module, leaving FHIRPathEngine.matches() in org.hl7.fhir.dstu2/utils/FHIRPathEngine.java to call raw String.matches(sw) without RegexTimeout protection while replaceMatches() was updated, allowing an unauthenticated attacker to trigger catastrophic regex backtracking and exhaust server CPU. This issue is fixed in version 6.9.10.
Weakness: CWE-1333
Which versions are affected by CVE-2026-55470?
8 open source packages ship an affected version, including ca.uhn.hapi.fhir:org.hl7.fhir.convertors, ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 and ca.uhn.hapi.fhir:org.hl7.fhir.validation. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
ca.uhn.hapi.fhir:org.hl7.fhir.convertors Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.convertors Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.dstu2 Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.validation Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.validation Maven | All versions | 6.9.10 |
2 more packages
ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli Maven | All versions | 6.9.10 |
ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli Maven | All versions | 6.9.10 |
Products include Hapifhir Hl7 Fhir Core.
How do I fix CVE-2026-55470?
Upgrade ca.uhn.hapi.fhir:org.hl7.fhir.convertors to 6.9.10 or later.
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-2026-55470 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55470 exists.
Other vulnerabilities in hapifhir org.hl7.fhir.core
- CVE-2026-34361 HAPI FHIR: Unauthenticated SSRF via /loadIG Chains with startsWith() Credential Leak for Authentication Token Theft
- CVE-2026-55471 HAPI FHIR: XXE in XsltUtilities.saxonTransform via unhardened Saxon TransformerFactory
- CVE-2023-24057 MITM based Zip Slip in `ca.uhn.hapi.fhir:org.hl7.fhir.core`
- CVE-2023-28465 HL7 FHIR Partial Path Zip Slip due to bypass of CVE-2023-24057
- CVE-2026-34359 HAPI FHIR: Authentication Credential Leakage via Improper URL Prefix Matching on HTTP Redirect in HAPI FHIR Core
Sources
Also known as GHSA-fxj4-p9xp-37v5, ROOT-APP-MAVEN-CVE-2026-55470.