CVE-2026-81876

High CVSS 7.5

Published 2026-09-16 · last changed 2026-09-17

The fix

We hold no Microsoft remediation data for CVE-2026-81876, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

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.

Sources

NVD record for CVE-2026-81876

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H