CVE-2026-100803
Full vulnerability record from the local CVENow database.
Description
Same-origin policy bypass in the WebExtensions component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Severity
HIGH
CVSS score
8.1
(v3.1)
Vulnerability status
Analyzed
Source identifier
Published
2026-09-29 13:17:45.390000
Last modified
2026-10-19 17:47:25.023000
View original CVE JSON
{
"id": "CVE-2026-100803",
"sourceIdentifier": "[email protected]",
"published": "2026-09-29T13:17:45.390",
"lastModified": "2026-10-19T17:47:25.023",
"vulnStatus": "Analyzed",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "Same-origin policy bypass in the WebExtensions component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17."
}
],
"affected": [
{
"source": "[email protected]",
"affectedData": [
{
"vendor": "Mozilla",
"product": "Firefox",
"versions": [
{
"version": "115.42",
"lessThanOrEqual": "115.*",
"versionType": "rpm",
"status": "unaffected"
},
{
"version": "140.17",
"lessThanOrEqual": "140.*",
"versionType": "rpm",
"status": "unaffected"
},
{
"version": "153.4",
"lessThanOrEqual": "153.*",
"versionType": "rpm",
"status": "unaffected"
},
{
"version": "157",
"lessThanOrEqual": "*",
"versionType": "rpm",
"status": "unaffected"
}
]
},
{
"vendor": "Mozilla",
"product": "Thunderbird",
"versions": [
{
"version": "140.17",
"lessThanOrEqual": "140.*",
"versionType": "rpm",
"status": "unaffected"
},
{
"version": "153.4",
"lessThanOrEqual": "153.*",
"versionType": "rpm",
"status": "unaffected"
},
{
"version": "157",
"lessThanOrEqual": "*",
"versionType": "rpm",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
"baseScore": 8.1,
"baseSeverity": "HIGH",
"attackVector": "NETWORK",
"attackComplexity": "LOW",
"privilegesRequired": "NONE",
"userInteraction": "REQUIRED",
"scope": "UNCHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "NONE"
},
"exploitabilityScore": 2.8,
"impactScore": 5.2
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-10-01T15:15:51.082535Z",
"id": "CVE-2026-100803",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"weaknesses": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-346"
}
]
}
],
"configurations": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
"versionEndExcluding": "115.42.0",
"matchCriteriaId": "9D4A8C0D-2E00-4182-A7A2-0F669C935655"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
"versionStartIncluding": "116.0",
"versionEndExcluding": "140.17.0",
"matchCriteriaId": "A5443D2F-B495-4F49-BD35-79AE67BA1E1C"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
"versionStartIncluding": "141.0",
"versionEndExcluding": "153.4.0",
"matchCriteriaId": "59A9D6A8-7187-4134-8193-D0E325115773"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
"versionStartIncluding": "154.0.0",
"versionEndExcluding": "157.0.0",
"matchCriteriaId": "CC64A654-10B5-4600-9E71-A2B276C5EAC3"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*",
"versionEndExcluding": "140.17.0",
"matchCriteriaId": "D25C5E0F-CC93-48A0-A656-29450505E8C6"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*",
"versionStartIncluding": "141.0",
"versionEndExcluding": "153.4.0",
"matchCriteriaId": "90E6FA6F-4AD3-4A75-A02F-5B668644087B"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*",
"versionStartIncluding": "154.0",
"versionEndExcluding": "157.0",
"matchCriteriaId": "8A93E2FC-CEDC-4074-B587-70CD89C5BC2B"
}
]
}
]
}
],
"references": [
{
"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2057988",
"source": "[email protected]",
"tags": [
"Permissions Required"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-100/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-101/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-102/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-103/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-97/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-98/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
},
{
"url": "https://www.mozilla.org/security/advisories/mfsa2026-99/",
"source": "[email protected]",
"tags": [
"Vendor Advisory"
]
}
]
}