CVE-2026-4702
published 2026-03-24CVE-2026-4702: JIT miscompilation in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
PriorityP350critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.47%
37.9th percentile
JIT miscompilation in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected
10 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| debian | firefox-esr | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| debian | thunderbird | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| mozilla | firefox | < 140.9.0 | 140.9.0 |
| mozilla | firefox | < 149.0 | 149.0 |
| mozilla | firefox | — | — |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb11u1 | 1:140.9.0esr-1~deb11u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb12u1 | 1:140.9.0esr-1~deb12u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb13u1 | 1:140.9.0esr-1~deb13u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1 | 1:140.9.0esr-1 |
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
osv9.8CRITICAL
vendor_debian9.8CRITICAL
vendor_redhat9.8CRITICAL
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Red Hat
firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
vendor_redhat·2026-03-24·CVSS 9.8
CVE-2026-4702 [CRITICAL] CWE-733 firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
JIT miscompilation in the JavaScript Engine component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/thunderbird-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: firefox (Red Hat Enterprise Linux 6) - Out of support scope
Package: thunderbird (Red Hat Enterp
Debian
CVE-2026-4702: firefox - JIT miscompilation in the JavaScript Engine component. This vulnerability affect...
vendor_debian·2026·CVSS 9.8
CVE-2026-4702 [CRITICAL] CVE-2026-4702: firefox - JIT miscompilation in the JavaScript Engine component. This vulnerability affect...
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Scope: local
sid: resolved (fixed in 149.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4702
vendor_mozilla·CVSS 9.8
CVE-2026-4702 [CRITICAL] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4702
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4702
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4702
vendor_mozilla·CVSS 9.8
CVE-2026-4702 [CRITICAL] Mozilla Foundation Security Advisory 2026-24: CVE-2026-4702
Mozilla Foundation Security Advisory 2026-24
CVE: CVE-2026-4702
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4702
vendor_mozilla·CVSS 9.8
CVE-2026-4702 [CRITICAL] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4702
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4702
Product: Firefox
Impact: high
Fixed in: Firefox 149
Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4702
vendor_mozilla·CVSS 9.8
CVE-2026-4702 [CRITICAL] Mozilla Foundation Security Advisory 2026-22: CVE-2026-4702
Mozilla Foundation Security Advisory 2026-22
CVE: CVE-2026-4702
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.9
VulDB
Mozilla Firefox up to 148 JavaScript Engine type confusion (Nessus ID 303907 / WID-SEC-2026-0850)
vuldb·2026-04-16·CVSS 9.8
CVE-2026-4702 [CRITICAL] Mozilla Firefox up to 148 JavaScript Engine type confusion (Nessus ID 303907 / WID-SEC-2026-0850)
A vulnerability has been found in Mozilla Firefox up to 148 and classified as critical. Affected is an unknown function of the component JavaScript Engine. This manipulation causes type confusion.
This vulnerability is tracked as CVE-2026-4702. The attack is possible to be carried out remotely. No exploit exists.
The affected component should be upgraded.
GHSA
GHSA-mrrg-439g-x65p: JIT miscompilation in the JavaScript Engine component
ghsa_unreviewed·2026-03-24
CVE-2026-4702 [CRITICAL] CWE-843 GHSA-mrrg-439g-x65p: JIT miscompilation in the JavaScript Engine component
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
OSV
CVE-2026-4702: JIT miscompilation in the JavaScript Engine component
osv·2026-03-24·CVSS 9.8
CVE-2026-4702 [CRITICAL] CVE-2026-4702: JIT miscompilation in the JavaScript Engine component
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-4702 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-4702 [HIGH] CVE-2026-4702 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4702 :
NixOS vulnerability analysis and mitigation
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Source : NVD
## 9.8
Score
Published March 24, 2026
Severity CRITICAL
CNA Score 9.8
Affected Technologies
NixOS
Mozilla Firefox
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 6
Exploitation Probability (EPSS) N/A
Affected packages and libraries
rhel10::thunderbird-flatpak
rhel10::thunderbird-flatpak.src
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Mar 31, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Mar 31, 2026
Chainguard Has Fix Added at: Mar
Bugzilla
CVE-2026-4702 firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
bugzilla·2026-03-24·CVSS 9.8
CVE-2026-4702 [CRITICAL] CVE-2026-4702 firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
CVE-2026-4702 firefox: thunderbird: JIT miscompilation in the JavaScript Engine component
JIT miscompilation in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
Discussion:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:5931 https://access.redhat.com/errata/RHSA-2026:5931
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2026:5930 https://access.redhat.com/errata/RHSA-2026:5930
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2026:5932 https://access.redhat.com/errata/RHSA-2026:5932
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2
2026-03-24
Published