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CVE-2026-84143— Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15

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存在安全漏洞，该漏洞源于内存损坏或其他安全相关缺陷，可能被利用。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.38% · P31

Affected Version Matrix 6

VendorProduct Version RangeStatus
Mozilla Firefox 140.15≤ 140.* unaffected
153.2≤ 153.* unaffected
155≤ * unaffected
Mozilla Thunderbird 140.15≤ 140.* unaffected
153.2≤ 153.* unaffected
155≤ * unaffected
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I. Basic Information for CVE-2026-84143

Vulnerability Information
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Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15
Source: CVE Program / CVE List V5
Vulnerability Description
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, 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存在安全漏洞，该漏洞源于内存损坏或其他安全相关缺陷，可能被利用。
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 140.15 ~ 140.* -
Mozilla Thunderbird 140.15 ~ 140.* -

II. Public POCs for CVE-2026-84143

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III. Intelligence Information for CVE-2026-84143

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Vendor Advisories for CVE-2026-84143 (6)

Other References for CVE-2026-84143 (2)

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-2026-84143

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