CVE-2026-84642 (GCVE-0-2026-84642)
Vulnerability from cvelistv5
Published
2026-09-01 21:33
Modified
2026-09-02 19:14
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Summary
The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.
References
Impacted products
Vendor Product Version
Mozilla Thunderbird Unaffected: 153.2
Unaffected: 155
 Create a notification for this product.
Show details on NVD website

To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-84642",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-02T19:14:05.007405Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-1333",
                "description": "CWE-1333 Inefficient Regular Expression Complexity",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-02T19:14:29.482Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "Thunderbird",
          "vendor": "Mozilla",
          "versions": [
            {
              "lessThanOrEqual": "153.*",
              "status": "unaffected",
              "version": "153.2",
              "versionType": "rpm"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "155",
              "versionType": "rpm"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "ChinhNguyen, Lowk3yz"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2."
            }
          ],
          "value": "The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-01T21:44:16.162Z",
        "orgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
        "shortName": "mozilla"
      },
      "references": [
        {
          "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2060462"
        },
        {
          "url": "https://www.mozilla.org/security/advisories/mfsa2026-86/"
        },
        {
          "url": "https://www.mozilla.org/security/advisories/mfsa2026-88/"
        }
      ],
      "title": "Allowed UNC hostnames for attachments interpreted as a regular expression"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
    "assignerShortName": "mozilla",
    "cveId": "CVE-2026-84642",
    "datePublished": "2026-09-01T21:33:07.987Z",
    "dateReserved": "2026-09-01T21:33:07.702Z",
    "dateUpdated": "2026-09-02T19:14:29.482Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-84642\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-02T19:14:05.007405Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-1333\", \"description\": \"CWE-1333 Inefficient Regular Expression Complexity\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-02T19:14:26.172Z\"}}], \"cna\": {\"title\": \"Allowed UNC hostnames for attachments interpreted as a regular expression\", \"credits\": [{\"lang\": \"en\", \"value\": \"ChinhNguyen, Lowk3yz\"}], \"affected\": [{\"vendor\": \"Mozilla\", \"product\": \"Thunderbird\", \"versions\": [{\"status\": \"unaffected\", \"version\": \"153.2\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"153.*\"}, {\"status\": \"unaffected\", \"version\": \"155\", \"versionType\": \"rpm\", \"lessThanOrEqual\": \"*\"}]}], \"references\": [{\"url\": \"https://bugzilla.mozilla.org/show_bug.cgi?id=2060462\"}, {\"url\": \"https://www.mozilla.org/security/advisories/mfsa2026-86/\"}, {\"url\": \"https://www.mozilla.org/security/advisories/mfsa2026-88/\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"The values of the mail.allowed_attachment_hostnames advanced config setting were used in a regular expression without escaping. For some possible valid hostnames, this could allow certain unintended hostnames to also match and serve remote attachments. This vulnerability was fixed in Thunderbird 155 and Thunderbird 153.2.\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"f16b083a-5664-49f3-a51e-8d479e5ed7fe\", \"shortName\": \"mozilla\", \"dateUpdated\": \"2026-09-01T21:44:16.162Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-84642\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-02T19:14:29.482Z\", \"dateReserved\": \"2026-09-01T21:33:07.702Z\", \"assignerOrgId\": \"f16b083a-5664-49f3-a51e-8d479e5ed7fe\", \"datePublished\": \"2026-09-01T21:33:07.987Z\", \"assignerShortName\": \"mozilla\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.