Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Remotely reachable DEFLATE decompression bomb needing no auth or interaction, with availability-only impact (heap exhaustion / process termination) and no confidentiality or integrity effect.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
4DescriptionCVE.org
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 consume attacker-controlled Smart Health Card JWT content whose header contains zip: "DEF" and whose small raw-DEFLATE payload expands to a very large value. SHCParser.decodeJWT() passes the decoded payload to SHCParser.inflate(), which accumulates all decompressed bytes in a ByteArrayOutputStream without an output-size limit before JSON parsing, and SHCParser.decompress() contains the same unbounded pattern. An application or validator service that accepts attacker-supplied SHC content can therefore suffer excessive heap allocation, severe garbage-collection pressure, request failure, process instability, or process termination. This issue is fixed in version 6.9.12.
AnalysisAI
Unbounded DEFLATE decompression in HAPI FHIR's SHCParser (org.hl7.fhir.core prior to 6.9.12) allows an unauthenticated remote attacker to exhaust heap memory by submitting a small Smart Health Card JWT whose header sets zip:"DEF" and whose compressed payload inflates to an arbitrarily large size, resulting in severe garbage-collection pressure, request failure, process instability, or process termination. The issue is confined to the decompression path in SHCParser.decodeJWT(), SHCParser.inflate() and SHCParser.decompress(), which accumulate all output in a ByteArrayOutputStream before any size check occurs; no public exploit code was identified at time of analysis and the flaw is not confirmed actively exploited (CISA KEV), though no EPSS estimate was supplied in the source data. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the application or validator built on org.hl7.fhir.core (versions prior to 6.9.12) accepts attacker-supplied Smart Health Card content and routes it through SHCParser - i.e., an exposed SHC/JWT parsing or validation path. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine but bounded denial-of-service issue, not a high-impact compromise despite the 7.5 'High' rating. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patch: 6.9.12 - upgrade org.hl7.fhir.core (HAPI FHIR core) to version 6.9.12 or later, as published at https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.12, where the decompression path is given an output-size limit; the underlying change is in PR #2493 (commit fbb94216e0ad21ded75be77e5e20242ba194e83f) and the advisory at https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr should be used to drive internal tracking. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all applications and services using org.hl7.fhir.core prior to 6.9.12 and identify endpoints that accept external SHC/JWT content; immediately block or restrict those SHCParser paths at the API gateway or WAF, reject JWT headers with zip:'DEF', and enforce strict request body limits. …
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External POC / Exploit Code
Leaving vuln.today
EUVD-2026-80993