CVE-2025-62494

Full vulnerability record from the local CVENow database.

Description

A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine. * The code first checks if the left-hand operand is a string. * It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf). * During this callback, an attacker can modify the type of the left-hand operand in memory, changing it from a string to a different type (e.g., an object or an array). * The code then proceeds to call JS_ConcatStringInPlace, which still treats the modified left-hand value as a string. This mismatch between the assumed type (string) and the actual type allows an attacker to control the data structure being processed by the concatenation logic, resulting in a type confusion condition. This can lead to out-of-bounds memory access, potentially resulting in memory corruption and arbitrary code execution in the context of the QuickJS runtime.

Severity

HIGH

CVSS score

7.1 (v4.0)

Vulnerability status

Analyzed

Source identifier

[email protected]

Published

2025-10-16 16:15:39.943000

Last modified

2026-10-19 16:10:00.260000

View original CVE JSON

{
  "id": "CVE-2025-62494",
  "sourceIdentifier": "[email protected]",
  "published": "2025-10-16T16:15:39.943",
  "lastModified": "2026-10-19T16:10:00.260",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine.\n\n  *  The code first checks if the left-hand operand is a string.\n\n\n  *  It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf).\n\n\n  *  During this callback, an attacker can modify the type of the left-hand operand in memory, changing it from a string to a different type (e.g., an object or an array).\n\n\n  *  The code then proceeds to call JS_ConcatStringInPlace, which still treats the modified left-hand value as a string.\n\n\nThis mismatch between the assumed type (string) and the actual type allows an attacker to control the data structure being processed by the concatenation logic, resulting in a type confusion condition. This can lead to out-of-bounds memory access, potentially resulting in memory corruption and arbitrary code execution in the context of the QuickJS runtime."
    },
    {
      "lang": "es",
      "value": "Existe una vulnerabilidad de confusión de tipos en el manejo de la operación de adición de cadenas (+) dentro del motor QuickJS.\n\n  * El código primero verifica si el operando de la izquierda es una cadena.\n\n  * Luego intenta convertir el operando de la derecha a un valor primitivo usando JS_ToPrimitiveFree. Esta conversión puede activar una devolución de llamada (por ejemplo, toString o valueOf).\n\n  * Durante esta devolución de llamada, un atacante puede modificar el tipo del operando de la izquierda en memoria, cambiándolo de una cadena a un tipo diferente (por ejemplo, un objeto o un array).\n\n  * El código luego procede a llamar a JS_ConcatStringInPlace, que aún trata el valor de la izquierda modificado como una cadena.\n\nEste desajuste entre el tipo asumido (cadena) y el tipo real permite a un atacante controlar la estructura de datos que está siendo procesada por la lógica de concatenación, lo que resulta en una condición de confusión de tipos. Esto puede llevar a un acceso a memoria fuera de límites, lo que podría resultar en corrupción de memoria y ejecución de código arbitrario en el contexto del entorno de ejecución de QuickJS."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "QuickJS",
          "product": "QuickJS",
          "defaultStatus": "unaffected",
          "collectionURL": "https://bellard.org/quickjs/",
          "packageName": "JS_ConcatStringInPlace",
          "versions": [
            {
              "version": "2025-04-26",
              "lessThan": "2025-09-13",
              "versionType": "date",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
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        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "4.0",
          "vectorString": "CVSS:4.0/AV:A/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L/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",
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          "attackVector": "ADJACENT",
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          "subAvailabilityImpact": "LOW",
          "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"
        }
      }
    ],
    "cvssMetricV31": [
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          "baseSeverity": "HIGH",
          "attackVector": "ADJACENT_NETWORK",
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          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
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        "impactScore": 5.9
      }
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      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2025-10-16T17:46:18.542287Z",
          "id": "CVE-2025-62494",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-704"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
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  "references": [
    {
      "url": "https://bellard.org/quickjs/Changelog",
      "source": "[email protected]",
      "tags": [
        "Release Notes"
      ]
    },
    {
      "url": "https://issuetracker.google.com/434193023",
      "source": "[email protected]",
      "tags": [
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        "Issue Tracking"
      ]
    }
  ]
}