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Fencer Intel
high 7.5

CVE-2026-81876 json

HAPI FHIR: SHCParser DEFLATE infinite loop causes denial of service

published last mo. modified last mo. also EUVD-2026-80998 , GHSA-gq9c-wmrm-5hvr

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

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.

Patch / fix

  • maven ca.uhn.hapi.fhir:org.hl7.fhir.r5 6.9.12
  • maven ca.uhn.hapi.fhir:org.hl7.fhir.validation 6.9.12
  • maven ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli 6.9.12
  • ca.uhn.hapi.fhir org.hl7.fhir.core 6.9.12
  • hapifhir hl7_fhir_core 6.9.12

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-gq9c-wmrm-5hvr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven ca.uhn.hapi.fhir:org.hl7.fhir.r5
<6.9.12
6.9.12
maven ca.uhn.hapi.fhir:org.hl7.fhir.validation
<6.9.12
6.9.12
maven ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli
<6.9.12
6.9.12

Affected products

  • hapifhir org.hl7.fhir.core

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-835 Loop with Unreachable Exit Condition

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.