CVE-2021-1616

{
  "id": "CVE-2021-1616",
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          "id": "CVE-2021-1616",
          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "none"
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              "automatable": "no"
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            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2024-11-07T21:40:27.260275Z"
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        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4.3,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:N/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": true
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    "cvssMetricV31": [
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        "type": "Secondary",
        "source": "psirt@cisco.com",
        "cvssData": {
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          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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        "impactScore": 1.4,
        "exploitabilityScore": 2.8
      },
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        "cvssData": {
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          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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        "impactScore": 1.4,
        "exploitabilityScore": 2.8
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  "affected": [
    {
      "source": "psirt@cisco.com",
      "affectedData": [
        {
          "vendor": "Cisco",
          "product": "Cisco IOS XE Software",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
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  ],
  "published": "2021-09-23T03:15:12.627",
  "references": [
    {
      "url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-h323alg-bypass-4vy2MP2Q",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "psirt@cisco.com"
    },
    {
      "url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-h323alg-bypass-4vy2MP2Q",
      "tags": [
        "Vendor Advisory"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "psirt@cisco.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-693"
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      "source": "nvd@nist.gov",
      "description": [
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          "lang": "en",
          "value": "NVD-CWE-Other"
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  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A vulnerability in the H.323 application level gateway (ALG) used by the Network Address Translation (NAT) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass the ALG. This vulnerability is due to insufficient data validation of traffic that is traversing the ALG. An attacker could exploit this vulnerability by sending crafted traffic to a targeted device. A successful exploit could allow the attacker to bypass the ALG and open connections that should not be allowed to a remote device located behind the ALG. Note: This vulnerability has been publicly discussed as NAT Slipstreaming."
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad en el gateway de nivel de aplicación H.323 (ALG) usada por la funcionalidad Network Address Translation (NAT) de Cisco IOS XE Software podría permitir a un atacante remoto no autenticado omitir la ALG. Esta vulnerabilidad es debido a una comprobación insuficiente de los datos del tráfico que atraviesa el ALG. Un atacante podría explotar esta vulnerabilidad mediante el envío de tráfico diseñado a un dispositivo objetivo. Una explotación con éxito podría permitir al atacante omitir el ALG y abrir conexiones que no deberían estar permitidas a un dispositivo remoto ubicado detrás del ALG. Nota: Esta vulnerabilidad ha sido discutida públicamente como NAT Slipstreaming"
    }
  ],
  "lastModified": "2026-06-17T03:32:10.500",
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  "sourceIdentifier": "psirt@cisco.com"
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