Vulnerability · NVD

CVE-2026-100803

CVE-2026-100803, high severity (CVSS 8.1): 2 tracked apps concerned, all fixed or indeterminable on their current version.

Severity (CVSS): 8.1
Exploitation: 0.2 %
Tracked apps: 2
Still exposed: 0

Published on 2026-09-29

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.

Attack vector : Network No privileges required

Show raw CVSS vector

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

EPSS 0.19% exploit very unlikely percentile 7.5%

Tracked apps referencing this CVE

For each app: the affected range, the fixing version, and where the tracked app stands today.

Mozilla Firefox Windows winget:Mozilla.Firefox

Affected <157 Fixed in 157 Latest tracked 157.0 patched

Observed affected builds (178)

156.0.1 156.0 155.0.1 155.0 154.0.1 154.0 153.0.4 153.0.3 153.0.1 153.0 152.0.6 152.0.5 152.0.4 152.0.3 152.0.2 152.0.1 152.0 151.0.4 151.0.3 151.0.2 151.0.1 151.0 150.0.3 150.0.2 150.0.1 150.0 149.0.2 149.0 148.0.2 148.0 +148 · see history
Mozilla Thunderbird Windows winget:Mozilla.Thunderbird

Affected <157 Fixed in 157 Latest tracked 157.0.1 patched

Observed affected builds (133)

156.0.1 156.0 155.0.1 155.0 154.0 153.0.3 153.0.2 153.0.1 153.0 152.0.1 152.0 151.0.1 151.0 150.0.2 150.0.1 150.0 149.0.2 149.0.1 149.0 148.0.1 148.0 147.0.2 147.0.1 147.0 146.0.1 146.0 145.0 144.0.1 144.0 143.0.1 +103 · see history

Vulnerable CPE configurations (2)

Vendor	Product	Platform	Versions	CPE 2.3 URI
mozilla	firefox All platforms (wildcard)	All platforms (wildcard)	<157	cpe:2.3:a:mozilla:firefox::::::::
mozilla	thunderbird All platforms (wildcard)	All platforms (wildcard)	<157	cpe:2.3:a:mozilla:thunderbird::::::::

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