CVE-2026-81876HAPI FHIR: SHCParser DEFLATE infinite loop causes denial of service

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.

CVSS

7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness (CWE)

CWE-20, CWE-400, CWE-835

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

0.63% (percentile 49)

Assigned by

GitHub_M

NVD analysis

Awaiting Analysis

Record last updated

Sep 17, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

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