TI-2026-56488 Aliases CVE-2026-81876 GHSA-gq9c-wmrm-5hvr

HAPI FHIR: SHCParser DEFLATE infinite loop causes denial of service

HIGH 72CWE-20Published 2026-09-16 · Updated 2026-09-17

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

HAPI FHIR is a complete implementation of the HL7 FHIR standard for healthcare interoperability in Java. Prior to version 6.9.12, SHCParser in org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/SHCParser.java can enter an infinite loop while processing attacker-controlled Smart Health Card JWT content whose header contains zip: "DEF" and whose raw-DEFLATE payload is empty or truncated. SHCParser.decodeJWT() reaches SHCParser.inflate(), where Inflater.inflate() can return zero while Inflater.finished() remains false and Inflater.needsInput() is true. The loop also lacks an Inflater.needsDictionary() termination check, SHCParser.decompress() contains the same zero-progress pattern, and ResourceChecker.java can reach SHC parsing during file-format detection. A malformed validation request can pin a JVM worker thread indefinitely, and concurrent requests can exhaust all validation workers. This issue is fixed in version 6.9.12.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.0063 50th percentileScored 2026-11-07

Fix Fixed org.hl7.fhir.core (hapifhir): 6.9.12ca.uhn.hapi.fhir:org.hl7.fhir.r5 (Maven): 6.9.12+2 more products

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
hapifhir	org.hl7.fhir.core	before 6.9.12	6.9.12	Patch available	CNA
—	ca.uhn.hapi.fhir:org.hl7.fhir.r5 (Maven)	before 6.9.12	6.9.12	Patch available	GHSA-gq9c-wmrm-5hvr
—	ca.uhn.hapi.fhir:org.hl7.fhir.validation (Maven)	before 6.9.12	6.9.12	Patch available	GHSA-gq9c-wmrm-5hvr
—	ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli (Maven)	before 6.9.12	6.9.12	Patch available	GHSA-gq9c-wmrm-5hvr

org.hl7.fhir.core Vendorhapifhir Affected before 6.9.12 Fixed in 6.9.12 Patch available CNA
ca.uhn.hapi.fhir:org.hl7.fhir.r5 (Maven) Vendor— Affected before 6.9.12 Fixed in 6.9.12 Patch available GHSA-gq9c-wmrm-5hvr
ca.uhn.hapi.fhir:org.hl7.fhir.validation (Maven) Vendor— Affected before 6.9.12 Fixed in 6.9.12 Patch available GHSA-gq9c-wmrm-5hvr
ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli (Maven) Vendor— Affected before 6.9.12 Fixed in 6.9.12 Patch available GHSA-gq9c-wmrm-5hvr

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:hapifhir:hl7_fhir_core::::::::	—	—	hapifhir

cpe:2.3:a:hapifhir:hl7_fhir_core:*:*:*:*:*:*:*:* Versions — — ·hapifhir

Remediation

Fix · CNA org.hl7.fhir.core (hapifhir) Fixed in 6.9.12
Fix · GHSA-gq9c-wmrm-5hvr ca.uhn.hapi.fhir:org.hl7.fhir.r5 (Maven) Fixed in 6.9.12 Advisory →
Fix · GHSA-gq9c-wmrm-5hvr ca.uhn.hapi.fhir:org.hl7.fhir.validation (Maven) Fixed in 6.9.12 Advisory →
Fix · GHSA-gq9c-wmrm-5hvr ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli (Maven) Fixed in 6.9.12 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-81876
2026-10-03 Alias added: GHSA-gq9c-wmrm-5hvr
2026-10-28 EPSS moved to the 50th–90th percentile

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-81876

Other 5

TI-2026-26647 HAPI FHIR: Unauthenticated SSRF via /loadIG Chains with startsWith() Credential Leak for Authentication Token Theft CVSS 3.1CRITICAL 9.3
TI-2026-40028 HAPI FHIR: XXE in XsltUtilities.saxonTransform via unhardened Saxon TransformerFactory CVSS 4.0HIGH 8.7
TI-2026-26645 HAPI FHIR: Authentication Credential Leakage via Improper URL Prefix Matching on HTTP Redirect in HAPI FHIR Core CVSS 3.1CRITICAL 9.1
TI-2026-56487 HAPI FHIR: SHCParser unbounded DEFLATE decompression causes denial of service CVSS 3.1HIGH 7.5
TI-2026-44485 HAPI FHIR: XHTML narrative parser unbounded recursion causes StackOverflow denial of service CVSS 3.1HIGH 7.5
TI-2026-44484 HAPI FHIR: JSON utility parser unbounded recursion causes StackOverflow denial of service CVSS 3.1HIGH 7.5

See all 17 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences