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

Quick assessment

Affected
hapifhir org.hl7.fhir.core
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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

CVSS 7.5 · High

Affected Version Matrix 1

VendorProduct Version RangeStatus
hapifhir org.hl7.fhir.core < 6.9.12 affected
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I. Basic Information for CVE-2026-81876

Vulnerability Information

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Vulnerability Title
HAPI FHIR: SHCParser DEFLATE infinite loop causes denial of service
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
hapifhir org.hl7.fhir.core < 6.9.12 -

II. Public POCs for CVE-2026-81876

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III. Intelligence Information for CVE-2026-81876

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Patches & Fixes for CVE-2026-81876 (3)

Other References for CVE-2026-81876 (1)

IV. Related Vulnerabilities

Same product: org.hl7.fhir.core
Same vendor: hapifhir
Same weakness: CWE-20

V. Comments for CVE-2026-81876

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