CVE-2026-4711
published 2026-03-24CVE-2026-4711: Use-after-free in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
PriorityP351critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.40%
32.1th percentile
Use-after-free in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected
6 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | — | — |
| debian | firefox-esr | — | — |
| debian | thunderbird | — | — |
| mozilla | firefox | < 140.9.0 | 140.9.0 |
| 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_debian9.8LOW
vendor_redhat9.8CRITICAL
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GHSA
GHSA-9979-85jw-xp9m: Use-after-free in the Widget: Cocoa component
ghsa_unreviewed·2026-03-24
CVE-2026-4711 [CRITICAL] CWE-416 GHSA-9979-85jw-xp9m: Use-after-free in the Widget: Cocoa component
Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
OSV
CVE-2026-4711: Use-after-free in the Widget: Cocoa component
osv·2026-03-24·CVSS 9.8
CVE-2026-4711 [CRITICAL] CVE-2026-4711: Use-after-free in the Widget: Cocoa component
Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Red Hat
firefox: thunderbird: Use-after-free in the Widget: Cocoa component
vendor_redhat·2026-03-24·CVSS 9.8
CVE-2026-4711 [CRITICAL] CWE-825 firefox: thunderbird: Use-after-free in the Widget: Cocoa component
firefox: thunderbird: Use-after-free in the Widget: Cocoa component
Use-after-free in the Widget: Cocoa 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:
Use-after-free in the Widget: Cocoa 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 Enterprise Linux 6) - Out of s
Debian
CVE-2026-4711: firefox - Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefo...
vendor_debian·2026·CVSS 9.8
CVE-2026-4711 [CRITICAL] CVE-2026-4711: firefox - Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefo...
Use-after-free in the Widget: Cocoa component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Scope: local
sid: resolved
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4711
vendor_mozilla·CVSS 9.8
CVE-2026-4711 [CRITICAL] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4711
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4711
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4711
vendor_mozilla·CVSS 9.8
CVE-2026-4711 [CRITICAL] Mozilla Foundation Security Advisory 2026-22: CVE-2026-4711
Mozilla Foundation Security Advisory 2026-22
CVE: CVE-2026-4711
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4711
vendor_mozilla·CVSS 9.8
CVE-2026-4711 [CRITICAL] Mozilla Foundation Security Advisory 2026-24: CVE-2026-4711
Mozilla Foundation Security Advisory 2026-24
CVE: CVE-2026-4711
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4711
vendor_mozilla·CVSS 9.8
CVE-2026-4711 [CRITICAL] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4711
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4711
Product: Firefox
Impact: high
Fixed in: Firefox 149
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-4711 firefox: thunderbird: Use-after-free in the Widget: Cocoa component
bugzilla·2026-03-24·CVSS 9.8
CVE-2026-4711 [CRITICAL] CVE-2026-4711 firefox: thunderbird: Use-after-free in the Widget: Cocoa component
CVE-2026-4711 firefox: thunderbird: Use-after-free in the Widget: Cocoa component
Use-after-free in the Widget: Cocoa 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-2026:6188 https:/
Wiz
CVE-2026-4711 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-4711 [HIGH] CVE-2026-4711 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4711 :
NixOS vulnerability analysis and mitigation
Use-after-free in the Widget: Cocoa 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
firefox
MozillaFirefox
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 29, 2026
Debian 11, 12, 13, 14 Severity CRIT
2026-03-24
Published