Vulnerability-Lookup

CVE-2026-81875 (GCVE-0-2026-81875)

Vulnerability from cvelistv5 – Published: 2026-09-16 18:44 – Updated: 2026-09-17 16:14

Title

HAPI FHIR: SHCParser unbounded DEFLATE decompression causes denial of service

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 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.

Severity

7.5 (High)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-17 16:14 UTC

CWE

CWE-20 - Improper Input Validation
CWE-400 - Uncontrolled Resource Consumption
CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)

Assigner

GitHub_M mitre root

References

5 references

URL	Tags
https://github.com/hapifhir/org.hl7.fhir.core/sec…	x_refsource_CONFIRM
https://github.com/hapifhir/org.hl7.fhir.core/pull/2493	x_refsource_MISC
https://github.com/hapifhir/org.hl7.fhir.core/com…	x_refsource_MISC
https://github.com/hapifhir/org.hl7.fhir.core/rel…	x_refsource_MISC
https://github.com/hapifhir/org.hl7.fhir.core/rel…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
hapifhir	org.hl7.fhir.core	Affected: < 6.9.12	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-81875

Vulnerability from fkie_nvd - Published: 2026-09-16 19:17 - Updated: 2026-09-17 17:16

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/hapifhir/org.hl7.fhir.core/commit/fbb94216e0ad21ded75be77e5e20242ba194e83f
	security-advisories@github.com	https://github.com/hapifhir/org.hl7.fhir.core/pull/2493
	security-advisories@github.com	https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.11
	security-advisories@github.com	https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.12
	security-advisories@github.com	https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "product": "org.hl7.fhir.core",
          "vendor": "hapifhir",
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    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/pull/2493"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.11"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.12"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        },
        {
          "lang": "en",
          "value": "CWE-400"
        },
        {
          "lang": "en",
          "value": "CWE-409"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-3W98-RRPR-FPRR

Vulnerability from github – Published: 2026-09-17 20:32 – Updated: 2026-09-17 20:32

Summary

HAPI FHIR: SHCParser unbounded DEFLATE decompression causes denial of service

Details

Summary

SHCParser inflates compressed Smart Health Card JWT payloads into memory without a decompressed-size limit. An attacker who can submit SHC content for validation can craft a small compressed JWT payload that expands to a very large byte array, causing memory exhaustion or severe garbage collection pressure.

Details

The vulnerable code is in org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/SHCParser.java.

decodeJWT() checks MAX_ALLOWED_SHC_LENGTH, but this only logs an error and parsing continues:

// SHCParser.java:282-284
if (jwt.length() > MAX_ALLOWED_SHC_LENGTH) {
  logError(...);
}

If the header contains "zip":"DEF", the payload is inflated before JSON parsing:

// SHCParser.java:300-304
if ("DEF".equals(res.header.asString("zip"))) {
  payloadJson = inflate(payloadJson);
}
res.payload = JsonParser.parseObject(FileUtilities.bytesToString(payloadJson), true);

inflate() accumulates all decompressed output in a ByteArrayOutputStream and has no maximum output size:

// SHCParser.java:455-468
while (!inflater.finished()) {
  final int count = inflater.inflate(buffer);
  outputStream.write(buffer, 0, count);
}
return outputStream.toByteArray();

The same unbounded decompression pattern exists in decompress() at SHCParser.java:410-423.

PoC

Create a highly compressible SHC-shaped JSON payload, compress it with raw DEFLATE (new Deflater(9, true)), Base64URL-encode it as the JWT payload, and set the JWT header to {"zip":"DEF"}.

Local verification measured the following expansion through SHCParser.inflate():

plain=1000066 compressed=1052 inflated=1000066 ratio=950
plain=16000066 compressed=15626 inflated=16000066 ratio=1023

A small compressed payload can therefore allocate many megabytes of heap. Larger payloads can trigger OutOfMemoryError or process instability.

Impact

This is a denial-of-service vulnerability. Any validator service or application that accepts attacker-supplied SHC content can be forced to allocate excessive heap memory. Impact ranges from request failure and severe GC pressure to process termination.

Credits

Thai Son Dinh from VinSOC Labs (R&D)

Severity

7.5 (High)


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

Show details on source website

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 6.9.11"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "ca.uhn.hapi.fhir:org.hl7.fhir.r5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.9.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 6.9.11"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "ca.uhn.hapi.fhir:org.hl7.fhir.validation"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.9.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "5.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-81875"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20",
      "CWE-400",
      "CWE-409"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T20:32:16Z",
    "nvd_published_at": "2026-09-16T19:17:44Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n`SHCParser` inflates compressed Smart Health Card JWT payloads into memory without a decompressed-size limit. An attacker who can submit SHC content for validation can craft a small compressed JWT payload that expands to a very large byte array, causing memory exhaustion or severe garbage collection pressure.\n\n### Details\nThe vulnerable code is in `org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/SHCParser.java`.\n\n`decodeJWT()` checks `MAX_ALLOWED_SHC_LENGTH`, but this only logs an error and parsing continues:\n\n```java\n// SHCParser.java:282-284\nif (jwt.length() \u003e MAX_ALLOWED_SHC_LENGTH) {\n  logError(...);\n}\n```\n\nIf the header contains `\"zip\":\"DEF\"`, the payload is inflated before JSON parsing:\n\n```java\n// SHCParser.java:300-304\nif (\"DEF\".equals(res.header.asString(\"zip\"))) {\n  payloadJson = inflate(payloadJson);\n}\nres.payload = JsonParser.parseObject(FileUtilities.bytesToString(payloadJson), true);\n```\n\n`inflate()` accumulates all decompressed output in a `ByteArrayOutputStream` and has no maximum output size:\n\n```java\n// SHCParser.java:455-468\nwhile (!inflater.finished()) {\n  final int count = inflater.inflate(buffer);\n  outputStream.write(buffer, 0, count);\n}\nreturn outputStream.toByteArray();\n```\n\nThe same unbounded decompression pattern exists in `decompress()` at `SHCParser.java:410-423`.\n\n### PoC\nCreate a highly compressible SHC-shaped JSON payload, compress it with raw DEFLATE (`new Deflater(9, true)`), Base64URL-encode it as the JWT payload, and set the JWT header to `{\"zip\":\"DEF\"}`.\n\nLocal verification measured the following expansion through `SHCParser.inflate()`:\n\n```text\nplain=1000066 compressed=1052 inflated=1000066 ratio=950\nplain=16000066 compressed=15626 inflated=16000066 ratio=1023\n```\n\nA small compressed payload can therefore allocate many megabytes of heap. Larger payloads can trigger `OutOfMemoryError` or process instability.\n\n### Impact\nThis is a denial-of-service vulnerability. Any validator service or application that accepts attacker-supplied SHC content can be forced to allocate excessive heap memory. Impact ranges from request failure and severe GC pressure to process termination.\n\n### Credits\n- Thai Son Dinh from VinSOC Labs (R\u0026D)",
  "id": "GHSA-3w98-rrpr-fprr",
  "modified": "2026-09-17T20:32:16Z",
  "published": "2026-09-17T20:32:16Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-3w98-rrpr-fprr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81875"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/pull/2493"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/commit/fbb94216e0ad21ded75be77e5e20242ba194e83f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.11"
    },
    {
      "type": "WEB",
      "url": "https://github.com/hapifhir/org.hl7.fhir.core/releases/tag/6.9.12"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "HAPI FHIR: SHCParser unbounded DEFLATE decompression causes denial of service"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

CVE-2026-81875 (GCVE-0-2026-81875)

FKIE_CVE-2026-81875

GHSA-3W98-RRPR-FPRR

Summary

Details

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