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CVE-2026-84140— Site isolation issue in the DOM: Navigation component

Quick assessment

Affected
Mozilla Firefox
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mozilla Firefox是Mozilla基金会开源的一款网页浏览器。 Mozilla Firefox 155之前版本、Firefox ESR 153.2之前版本、Thunderbird 155之前版本和Thunderbird 153.2之前版本存在安全漏洞，该漏洞源于DOM导航组件存在站点隔离问题。

AI Predicted 5.4 Difficulty: Moderate EPSS 0.18% · P8

Affected Version Matrix 4

VendorProduct Version RangeStatus
Mozilla Firefox 153.2≤ 153.* unaffected
155≤ * unaffected
Mozilla Thunderbird 153.2≤ 153.* unaffected
155≤ * unaffected
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I. Basic Information for CVE-2026-84140

Vulnerability Information
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Vulnerability Title
Site isolation issue in the DOM: Navigation component
Source: CVE Program / CVE List V5
Vulnerability Description
Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Mozilla Firefox 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mozilla Firefox是Mozilla基金会开源的一款网页浏览器。 Mozilla Firefox 155之前版本、Firefox ESR 153.2之前版本、Thunderbird 155之前版本和Thunderbird 153.2之前版本存在安全漏洞，该漏洞源于DOM导航组件存在站点隔离问题。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mozilla Firefox 153.2 ~ 153.* -
Mozilla Thunderbird 153.2 ~ 153.* -

II. Public POCs for CVE-2026-84140

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III. Intelligence Information for CVE-2026-84140

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Vendor Advisories for CVE-2026-84140 (4)

Same Patch Batch · Mozilla · 2026-09-01 · 34 CVEs total

CVE-2026-84122 Use-after-free in the Audio/Video component
CVE-2026-84130 Information disclosure in the Graphics: WebGPU component
CVE-2026-84129 Site isolation issue in the DOM: Navigation component
CVE-2026-84128 Privilege escalation in the WebDriver BiDi component
CVE-2026-84127 Information disclosure in the WebExtensions component in Firefox for Android
CVE-2026-84126 Incorrect boundary conditions in the Layout: Grid component
CVE-2026-84125 Use-after-free in the DOM: Core & HTML component
CVE-2026-84124 Use-after-free in the DOM: Core & HTML component
CVE-2026-84123 Privilege escalation due to use-after-free in the Graphics: WebGPU component
CVE-2026-84132 Information disclosure in the Networking: HTTP component
CVE-2026-84118 Use-after-free in the JavaScript: GC component
CVE-2026-84117 Privilege escalation in Firefox for Android
CVE-2026-84145 Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR
CVE-2026-84131 Privilege escalation due to invalid pointer in the Graphics component
CVE-2026-84121 Sandbox escape due to use-after-free in the DOM: Security component
CVE-2026-84120 Use-after-free in the Audio/Video component
CVE-2026-84119 Sandbox escape due to use-after-free in the DOM: Navigation component
CVE-2026-84642 Allowed UNC hostnames for attachments interpreted as a regular expression
CVE-2026-84133 Site isolation issue in the DOM: Push Subscriptions component
CVE-2026-84134 Other issue in the Profile Backup component

Showing top 20 of 34 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Firefox
Same vendor: Mozilla

V. Comments for CVE-2026-84140

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