CVE-2026-4723
published 2026-03-24CVE-2026-4723: Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.
PriorityP346critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.39%
32.0th percentile
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149 and Thunderbird 149.
Affected
3 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| mozilla | firefox | < 149.0 | 149.0 |
| mozilla | firefox | — | — |
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: Use-after-free in the JavaScript Engine component
vendor_redhat·2026-03-24·CVSS 9.8
CVE-2026-4723 [CRITICAL] CWE-825 firefox: Use-after-free in the JavaScript Engine component
firefox: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
A flaw was found in Firefox. The Mozilla Foundation's Security Advisory describes the following issue:
Use-after-free 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: firefox (Red Hat Enterprise Linux 10) - Not affected
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Not affected
Package: firefox (Red Hat Enterprise Linux 6) - Not affected
Package: firefox (Red Hat Enterprise Linux 7) - Not affected
Package: firefox (Red Hat Enterprise Linux 8) - Not affected
Package: firefo
Debian
CVE-2026-4723: firefox - Use-after-free in the JavaScript Engine component. This vulnerability affects Fi...
vendor_debian·2026·CVSS 9.8
CVE-2026-4723 [CRITICAL] CVE-2026-4723: firefox - Use-after-free in the JavaScript Engine component. This vulnerability affects Fi...
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
Scope: local
sid: resolved (fixed in 149.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4723
vendor_mozilla·CVSS 9.8
CVE-2026-4723 [CRITICAL] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4723
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4723
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4723
vendor_mozilla·CVSS 9.8
CVE-2026-4723 [CRITICAL] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4723
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4723
Product: Firefox
Impact: high
Fixed in: Firefox 149
OSV
CVE-2026-4723: Use-after-free in the JavaScript Engine component
osv·2026-03-24·CVSS 9.8
CVE-2026-4723 [CRITICAL] CVE-2026-4723: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
GHSA
GHSA-c97j-hmj5-572h: Use-after-free in the JavaScript Engine component
ghsa_unreviewed·2026-03-24
CVE-2026-4723 [CRITICAL] CWE-416 GHSA-c97j-hmj5-572h: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149.
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-4723 firefox: Use-after-free in the JavaScript Engine component
bugzilla·2026-03-24·CVSS 9.8
CVE-2026-4723 [CRITICAL] CVE-2026-4723 firefox: Use-after-free in the JavaScript Engine component
CVE-2026-4723 firefox: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149.
Wiz
CVE-2026-4723 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 5.1
CVE-2026-4723 [MEDIUM] CVE-2026-4723 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4723 :
NixOS vulnerability analysis and mitigation
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 149 and Thunderbird < 149.
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) 5.3
Exploitation Probability (EPSS) N/A
Affected packages and libraries
firefox
thunderbird
Sources
Chainguard Has Fix Added at: Mar 29, 2026
Homebrew Severity CRITICAL Has Fix Added at: Mar 26, 2026
Nix Severity CRITICAL Has Fix Added at: Mar 26, 2026
Ubuntu 22.04 Severity MEDIUM No Fix Added at: Mar 29, 2026
Linux Severity CRI
2026-03-24
Published