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CVE-2026-18401

Full vulnerability record from the local CVENow database.

Description

The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service. No privileges or user interaction beyond the ability to submit data for parsing are required. This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x. Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.

Severity
MEDIUM
CVSS score
6.9 (v4.0)
Vulnerability status
Awaiting Analysis
Source identifier
36c7be3b-2937-45df-85ea-ca7133ea542c
Published
2026-08-04 15:16:29.900000
Last modified
2026-10-23 23:10:00.157000
View original CVE JSON 
{
  "id": "CVE-2026-18401",
  "sourceIdentifier": "36c7be3b-2937-45df-85ea-ca7133ea542c",
  "published": "2026-08-04T15:16:29.900",
  "lastModified": "2026-10-23T23:10:00.157",
  "vulnStatus": "Awaiting Analysis",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.\n\n\n\nThe synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.\n\n\n\nRoot cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.\n\n\n\nImpact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service.\n\n\n\nNo privileges or user interaction beyond the ability to submit data for parsing are required.\n\n\n\nThis issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x.\n\n\n\nVersions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0."
    },
    {
      "lang": "es",
      "value": "El analizador JSON no bloqueante (asíncrono) en jackson-core no aplica la restricción maxNumberLength definida en StreamReadConstraints (predeterminado: 1000 caracteres). Un atacante capaz de enviar JSON a una aplicación que utiliza la API del analizador asíncrono puede proporcionar un token numérico de longitud arbitraria, lo que lleva a una asignación excesiva de memoria y un posible agotamiento de la CPU, resultando en una denegación de servicio.\n\nEl analizador síncrono aplica este límite correctamente, por lo que la restricción se aplica de forma inconsistente dependiendo de qué API de análisis utilice la aplicación.\n\nCausa raíz: la ruta de análisis asíncrono en NonBlockingUtf8JsonParserBase y clases relacionadas nunca invoca los métodos de validación de longitud de números. Los métodos de análisis de números como _finishNumberIntegralPart() acumulan dígitos en el TextBuffer sin ninguna verificación de longitud, luego llaman a _valueComplete() para finalizar el token. _valueComplete() no llama a resetInt() ni a resetFloat(), que son los métodos en ParserBase donde se realizan validateIntegerLength() y validateFPLength(). Debido a que ese paso de validación se omite, maxNumberLength nunca se aplica en la ruta de código asíncrono.\n\nImpacto: un atacante que envía un documento JSON que contiene un número arbitrariamente largo a una aplicación que utiliza el analizador asíncrono (por ejemplo, una aplicación Spring WebFlux u otra aplicación reactiva) puede causar una asignación ilimitada en el TextBuffer y un OutOfMemoryError. Si la aplicación posteriormente llama a getBigIntegerValue() o getDecimalValue(), la JVM puede además quedar ocupada en el análisis de BigInteger en O(n^2), causando una denegación de servicio basada en CPU.\n\nNo se requieren privilegios ni interacción del usuario más allá de la capacidad de enviar datos para su análisis.\n\nEste problema afecta a com.fasterxml.jackson.core:jackson-core desde la versión 2.15.0 hasta la 2.18.5 y desde la 2.19.0 hasta la 2.21.0, y a tools.jackson.core:jackson-core desde la 3.0.0 hasta la 3.0.x.\n\nLas versiones anteriores a la 2.15.0 no se ven afectadas, porque StreamReadConstraints -- que define la configuración maxNumberLength -- se introdujo por primera vez en jackson-core 2.15.0, por lo que no existe tal restricción que pueda ser eludida en versiones anteriores. Tenga en cuenta que GHSA-72hv-8253-57qq registra el límite inferior del rango 2.x afectado como 2.0.0."
    }
  ],
  "affected": [
    {
      "source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
      "affectedData": [
        {
          "vendor": "FasterXML",
          "product": "jackson-core",
          "defaultStatus": "unaffected",
          "collectionURL": "https://repo.maven.apache.org/maven2",
          "packageName": "com.fasterxml.jackson.core:jackson-core",
          "programFiles": [
            "src/main/java/com/fasterxml/jackson/core/json/async/NonBlockingUtf8JsonParserBase.java"
          ],
          "programRoutines": [
            {
              "name": "NonBlockingUtf8JsonParserBase._finishNumberIntegralPart"
            },
            {
              "name": "NonBlockingUtf8JsonParserBase._valueComplete"
            }
          ],
          "repo": "https://github.com/FasterXML/jackson-core",
          "versions": [
            {
              "version": "2.15.0",
              "lessThanOrEqual": "2.18.5",
              "versionType": "maven",
              "status": "affected"
            },
            {
              "version": "2.18.6",
              "versionType": "maven",
              "status": "unaffected"
            },
            {
              "version": "2.19.0",
              "lessThan": "2.21.1",
              "versionType": "maven",
              "status": "affected"
            },
            {
              "version": "2.21.1",
              "versionType": "maven",
              "status": "unaffected"
            }
          ]
        },
        {
          "vendor": "FasterXML",
          "product": "jackson-core",
          "defaultStatus": "unaffected",
          "collectionURL": "https://repo.maven.apache.org/maven2",
          "packageName": "tools.jackson.core:jackson-core",
          "programFiles": [
            "src/main/java/tools/jackson/core/json/async/NonBlockingUtf8JsonParserBase.java"
          ],
          "programRoutines": [
            {
              "name": "NonBlockingUtf8JsonParserBase._finishNumberIntegralPart"
            },
            {
              "name": "NonBlockingUtf8JsonParserBase._valueComplete"
            }
          ],
          "repo": "https://github.com/FasterXML/jackson-core",
          "versions": [
            {
              "version": "3.0.0",
              "lessThan": "3.1.0",
              "versionType": "maven",
              "status": "affected"
            },
            {
              "version": "3.1.0",
              "versionType": "maven",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
      {
        "source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
        "type": "Secondary",
        "cvssData": {
          "version": "4.0",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnAvailabilityImpact": "LOW",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "subAvailabilityImpact": "NONE",
          "exploitMaturity": "NOT_DEFINED",
          "confidentialityRequirement": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "valueDensity": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED"
        }
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-08-04T17:58:30.797291Z",
          "id": "CVE-2026-18401",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "36c7be3b-2937-45df-85ea-ca7133ea542c",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e887cd52cf",
      "source": "36c7be3b-2937-45df-85ea-ca7133ea542c"
    },
    {
      "url": "https://github.com/FasterXML/jackson-core/pull/1555",
      "source": "36c7be3b-2937-45df-85ea-ca7133ea542c"
    },
    {
      "url": "https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq",
      "source": "36c7be3b-2937-45df-85ea-ca7133ea542c"
    },
    {
      "url": "https://github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ]
}