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CVE-2026-4701— Use-after-free in the JavaScript Engine 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等都是美国Mozilla基金会的产品。Mozilla Firefox是一款开源Web浏览器。Mozilla Firefox ESR是Firefox(Web浏览器)的一个延长支持版本。Mozilla Thunderbird是一套从Mozilla Application Suite独立出来的电子邮件客户端软件。 Mozilla多款产品存在资源管理错误漏洞，该漏洞源于JavaScript引擎组件存在释放后重用。以下产品及版本受到影响：Firefox 149之前版本、Firefox

AI Predicted 8.1 Difficulty: Moderate EPSS 0.46% · P38

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 4

VendorProduct Version RangeStatus
Mozilla Firefox 140.9≤ 140.* unaffected
149≤ * unaffected
Mozilla Thunderbird 140.9≤ 140.* unaffected
149≤ * unaffected
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I. Basic Information for CVE-2026-4701

Vulnerability Information
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Vulnerability Title
Use-after-free in the JavaScript Engine component
Source: CVE Program / CVE List V5
Vulnerability Description
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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多款产品 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mozilla Firefox等都是美国Mozilla基金会的产品。Mozilla Firefox是一款开源Web浏览器。Mozilla Firefox ESR是Firefox(Web浏览器)的一个延长支持版本。Mozilla Thunderbird是一套从Mozilla Application Suite独立出来的电子邮件客户端软件。 Mozilla多款产品存在资源管理错误漏洞，该漏洞源于JavaScript引擎组件存在释放后重用。以下产品及版本受到影响：Firefox 149之前版本、Firefox
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 140.9 ~ 140.* -
Mozilla Thunderbird 140.9 ~ 140.* -

II. Public POCs for CVE-2026-4701

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III. Intelligence Information for CVE-2026-4701

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Vendor Advisories for CVE-2026-4701 (5)

Same Patch Batch · Mozilla · 2026-03-24 · 47 CVEs total

CVE-2026-4715 Uninitialized memory in the Graphics: Canvas2D component
CVE-2026-4727 Denial-of-service in the Libraries component in NSS
CVE-2026-4728 Spoofing issue in the Privacy: Anti-Tracking component
CVE-2026-4719 Incorrect boundary conditions in the Graphics: Text component
CVE-2026-4729 Memory safety bugs fixed in Firefox 149 and Thunderbird 149
CVE-2026-4721 Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9,
CVE-2026-3889 Spoofing issue in Thunderbird
CVE-2026-4371 Out of bounds read in IMAP parsing
CVE-2026-4720 Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thun
CVE-2026-4716 Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component
CVE-2026-4717 Privilege escalation in the Netmonitor component
CVE-2026-4714 Incorrect boundary conditions in the Audio/Video component
CVE-2026-4713 Incorrect boundary conditions in the Graphics component
CVE-2026-4725 Sandbox escape due to use-after-free in the Graphics: Canvas2D component
CVE-2026-4712 Information disclosure in the Widget: Cocoa component
CVE-2026-4710 Incorrect boundary conditions in the Audio/Video component
CVE-2026-4711 Use-after-free in the Widget: Cocoa component
CVE-2026-4709 Incorrect boundary conditions in the Audio/Video: GMP component
CVE-2026-4708 Incorrect boundary conditions in the Graphics component
CVE-2026-4707 Incorrect boundary conditions in the Graphics: Canvas2D component

Showing top 20 of 47 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Firefox
Same vendor: Mozilla

V. Comments for CVE-2026-4701

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