Vulnerabilities in pkg:maven/ca.uhn.hapi.fhir/org.hl7.fhir.r5

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gq9c-wmrm-5hvr",
  "modified" : "2026-09-17T20:32:21Z",
  "published" : "2026-09-17T20:32:21Z",
  "aliases" : [ "CVE-2026-81876" ],
  "summary" : "HAPI FHIR: SHCParser DEFLATE infinite loop causes denial of service",
  "details" : "### Summary\nA malformed Smart Health Card (SHC) JWT with `zip: \"DEF\"` and an empty or truncated DEFLATE payload causes `SHCParser.inflate()` to loop forever. This allows an attacker who can submit SHC content for validation to pin a JVM worker thread indefinitely, causing denial of service.\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()` inflates the JWT payload when the header contains `\"zip\":\"DEF\"`:\n\n```java\n// SHCParser.java:300-302\nif (\"DEF\".equals(res.header.asString(\"zip\"))) {\n  payloadJson = inflate(payloadJson);\n}\n```\n\n`inflate()` loops only on `!inflater.finished()` and does not check `inflater.needsInput()`, `inflater.needsDictionary()`, or zero-progress output:\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}\n```\n\nFor empty or truncated raw DEFLATE input, `Inflater.inflate()` returns `0`, `finished()` remains `false`, and `needsInput()` becomes `true`, producing an infinite tight loop. The same unsafe loop pattern also exists in `decompress()` at `SHCParser.java:410-423`.\n\nThe validator reaches this path during SHC validation and during file-format detection for SHC-looking input (`ResourceChecker.java:115-118`).\n\n### PoC\nCompile the project, then run a minimal local harness that calls:\n\n```java\nSHCParser.inflate(new byte[0]);\n```\n\nThis never returns. Local verification:\n\n```bash\ntimeout 3s java -cp ... VerifyDoSFindings shcHang\necho $?\n# 124 = timeout killed the hung process\n```\n\nA JWT PoC uses:\n\n- header: Base64URL(`{\"zip\":\"DEF\"}`)\n- payload: empty or truncated raw DEFLATE bytes\n- signature: arbitrary\n\nSubmit the resulting token as SHC content, for example via a `.shc` file or content beginning with `shc:/` that reaches the validator's SHC detection path.\n\n### Impact\nThis is a denial-of-service vulnerability. A single malformed SHC validation request can consume a worker thread indefinitely. In services that validate uploaded SHC content, a small number of concurrent malformed requests can exhaust all validation workers.\n\n### Credits\n- Thai Son Dinh from VinSOC Labs (R&D)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "ca.uhn.hapi.fhir:org.hl7.fhir.r5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.9.12"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.9.11"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "ca.uhn.hapi.fhir:org.hl7.fhir.validation"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.9.12"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.9.11"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "ca.uhn.hapi.fhir:org.hl7.fhir.validation.cli"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.9.12"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.9.11"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/hapifhir/org.hl7.fhir.core/security/advisories/GHSA-gq9c-wmrm-5hvr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-81876"
  }, {
    "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/d804558bd77372b1629e55a5b901cad3f5134cdc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/hapifhir/org.hl7.fhir.core/commit/edd5d8c139e669e39270785f08be7b63aefef24c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/hapifhir/org.hl7.fhir.core"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-400", "CWE-835" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-17T20:32:21Z",
    "nvd_published_at" : "2026-09-16T19:17:44Z"
  }
}