CVE-2026-4702

JIT miscompilation in the JavaScript Engine component

Severity Score

9.8

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Attend

*SSVC

Descriptions

JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

Compilación JIT errónea en el componente del motor JavaScript. Esta vulnerabilidad afecta a Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, y Thunderbird < 140.9.

JIT miscompilation in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

*Credits: Evyatar Ben Asher, Keane Lucas, Nicholas Carlini, Newton Cheng, Daniel Freeman, Alex Gaynor, and Joel Weinberger using Claude from Anthropic

CVSS Scores

NISTv3.1 9.8

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Attend

Exploitation

None

Automatable

Yes

Tech. Impact

Total

* Organization's Worst-case Scenario

Timeline

2026-03-23 CVE Reserved
2026-03-24 CVE Published
2026-04-13 CVE Updated
2026-04-25 EPSS Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

CAPEC

References (4)

URL	Tag	Source
https://www.mozilla.org/security/advisories/mfsa2026-23
https://www.mozilla.org/security/advisories/mfsa2026-24

URL	Date	SRC

URL	Date	SRC

URL	Date	SRC
https://www.mozilla.org/security/advisories/mfsa2026-20	2026-03-24
https://www.mozilla.org/security/advisories/mfsa2026-22	2026-03-24

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				< 140.9.0 Search vendor "Mozilla" for product "Firefox" and version " < 140.9.0"		esr		Affected
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				< 149.0 Search vendor "Mozilla" for product "Firefox" and version " < 149.0"		-		Affected