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CVE-2026-40685

Estado: AnalizadaCrítica (9.8)—

In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

AV:N/PR:N/UI:N: vulnerabilidad remota sin autenticación. Heap write OOB en procesamiento de JSON permite ejecución de código o escalada. Exim es servicio expuesto en red.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Application Isolation and SandboxingExploit ProtectionUpdate SoftwareVulnerability ScanningThreat Intelligence ProgramPrivileged Account Management

Tecnologías afectadas (1)

Exim — Exim

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-40685",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-40685",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-05-01T14:26:30.902958Z"
        }
      }
    ],
    "cvssMetricV31": [
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          "attackVector": "NETWORK",
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          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 4.2,
        "exploitabilityScore": 2.2
      },
      {
        "type": "Primary",
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        "cvssData": {
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          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
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          "versions": [
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              "version": "0",
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              "versionType": "semver"
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  "published": "2026-04-30T22:16:25.633",
  "references": [
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      "url": "https://code.exim.org/exim/exim/commit/9fdc057e71b87c87a0d3d2288b2810a0efaaba57",
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      "tags": [
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      "source": "cve@mitre.org"
    },
    {
      "url": "https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40685.assessment",
      "tags": [
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      "source": "cve@mitre.org"
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      "tags": [
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  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "lang": "en",
      "value": "In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \\ skipping."
    }
  ],
  "lastModified": "2026-06-17T10:45:34.323",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "versionEndExcluding": "4.99.2"
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}