CVE-2026-100803

HighCVSS 8.1/10Last modified Oct 19, 2026

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.

Metrics

CVSS 3.1 8.1/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Weakness enumeration

CWE-346

Affected software

VendorProductVersions
MozillaFirefox—
MozillaThunderbird—

References

Timeline

Published
Sep 29, 2026
Last modified
Oct 19, 2026
NVD status
Analyzed

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CVE-2026-100803: High severity, CVSS 8.1 | Vulnix