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CVE-2017-7764

Status: ModifiedMedium (5.3)—

Characters from the "Canadian Syllabics" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw "punycode" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from "Aspirational Use Scripts" such as Canadian Syllabics to be mixed with Latin characters in the "moderately restrictive" IDN profile. We have changed Firefox behavior to match the upcoming Unicode version 10.0 which removes this category and treats them as "Limited Use Scripts.". This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (3)

Debian — Debian LinuxMozilla — FirefoxMozilla — Thunderbird

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2017-7764",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:N/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
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    "cvssMetricV30": [
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        "cvssData": {
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          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
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  },
  "affected": [
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              "versionType": "custom"
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        }
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    }
  ],
  "published": "2018-06-11T21:29:08.437",
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      "tags": [
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      "tags": [
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  "vulnStatus": "Modified",
  "weaknesses": [
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      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
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  "descriptions": [
    {
      "lang": "en",
      "value": "Characters from the \"Canadian Syllabics\" unicode block can be mixed with characters from other unicode blocks in the addressbar instead of being rendered as their raw \"punycode\" form, allowing for domain name spoofing attacks through character confusion. The current Unicode standard allows characters from \"Aspirational Use Scripts\" such as Canadian Syllabics to be mixed with Latin characters in the \"moderately restrictive\" IDN profile. We have changed Firefox behavior to match the upcoming Unicode version 10.0 which removes this category and treats them as \"Limited Use Scripts.\". This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2."
    },
    {
      "lang": "es",
      "value": "Los caracteres del bloque unicode \"Canadian Syllabics\" pueden mezclarse con caracteres de otros bloques unicode en la barra de direcciones en lugar de ser presentados en su forma \"punycode\" sin procesar. Esto permite ataques de suplantación de nombres de dominio mediante la confusión de caracteres. El estándar Unicode actual permite que los caracteres \"Aspirational Use Scripts\" como Canadian Syllabics se mezclen con los caracteres latinos en el perfil IDN \"moderadamente restrictivo\". Se ha modificado el comportamiento de Firefox para que coincida con la inminente versión 10.0 de Unicode, que elimina esta categoría y los trata como \"Limited Use Scripts\". La vulnerabilidad afecta a Firefox en versiones anteriores a la 54, Firefox ESR en versiones anteriores a la 52.2 y Thunderbird en versiones anteriores a la 52.2."
    }
  ],
  "lastModified": "2026-06-17T01:25:09.023",
  "configurations": [
    {
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        {
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}