CVE-2026-4701 | Use-after-free in the JavaScript Engine component. This vuln… | CVSS 9.8 CRITICAL

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.

Metadata

CVE ID: CVE-2026-4701
State: PUBLISHED
Assigner: mozilla
Reserved: 2026-03-23 23:22 UTC
Published: 2026-03-24 12:30 UTC
Last updated: 2026-05-12 16:54 UTC
Primary CWE: CWE-416
CWE-416 Use After Free
Vendor / Product: Mozilla / Firefox
Sources: cve.org · NVD

Severity & Metrics

9.8 CRITICAL CVSS 3.1

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

SSVC — CISA Coordinator

Exploitation: none
Automatable: yes
Tech. Impact: total

Affected products (2)

Vendor	Product	Platform	Versions
Mozilla	Firefox	—	140.9 ≤ 140., 149 ≤
Mozilla	Thunderbird	—	140.9 ≤ 140., 149 ≤

Weakness (CWE)

CWE	Source	Description
CWE-416	adp	CWE-416 Use After Free

CVSS scores (1)

Score	Severity	Version	Source	Vector
9.8	CRITICAL	3.1	adp	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References (5)