CVE-2026-4696
published 2026-03-24CVE-2026-4696: Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149…
PriorityP350critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.48%
38.6th percentile
Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected
11 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 | < 115.34.0 | 115.34.0 |
| mozilla | firefox | < 149.0 | 149.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 128.0 < 140.9.0 | 140.9.0 |
| 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: Use-after-free in the Layout: Text and Fonts component
vendor_redhat·2026-03-24·CVSS 9.8
CVE-2026-4696 [CRITICAL] CWE-825 firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component
firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, 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 Layout: Text and Fonts 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: th
Debian
CVE-2026-4696: firefox - Use-after-free in the Layout: Text and Fonts component. This vulnerability affec...
vendor_debian·2026·CVSS 9.8
CVE-2026-4696 [CRITICAL] CVE-2026-4696: firefox - Use-after-free in the Layout: Text and Fonts component. This vulnerability affec...
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Scope: local
sid: resolved (fixed in 149.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4696
vendor_mozilla·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4696
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4696
Product: Firefox
Impact: high
Fixed in: Firefox 149
Mozilla
Mozilla Foundation Security Advisory 2026-21: CVE-2026-4696
vendor_mozilla·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Foundation Security Advisory 2026-21: CVE-2026-4696
Mozilla Foundation Security Advisory 2026-21
CVE: CVE-2026-4696
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 115.34
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4696
vendor_mozilla·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Foundation Security Advisory 2026-24: CVE-2026-4696
Mozilla Foundation Security Advisory 2026-24
CVE: CVE-2026-4696
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4696
vendor_mozilla·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Foundation Security Advisory 2026-22: CVE-2026-4696
Mozilla Foundation Security Advisory 2026-22
CVE: CVE-2026-4696
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4696
vendor_mozilla·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4696
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4696
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
VulDB
Mozilla Firefox up to 148 Fonts use after free (Nessus ID 303906 / WID-SEC-2026-0850)
vuldb·2026-04-16·CVSS 9.8
CVE-2026-4696 [CRITICAL] Mozilla Firefox up to 148 Fonts use after free (Nessus ID 303906 / WID-SEC-2026-0850)
A vulnerability labeled as critical has been found in Mozilla Firefox up to 148. This vulnerability affects unknown code of the component Fonts. The manipulation results in use after free.
This vulnerability is known as CVE-2026-4696. It is possible to launch the attack remotely. No exploit is available.
The affected component should be upgraded.
OSV
CVE-2026-4696: Use-after-free in the Layout: Text and Fonts component
osv·2026-03-24·CVSS 9.8
CVE-2026-4696 [CRITICAL] CVE-2026-4696: Use-after-free in the Layout: Text and Fonts component
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
GHSA
GHSA-h22r-8qx2-2mv3: Use-after-free in the Layout: Text and Fonts component
ghsa_unreviewed·2026-03-24
CVE-2026-4696 [CRITICAL] CWE-416 GHSA-h22r-8qx2-2mv3: Use-after-free in the Layout: Text and Fonts component
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-4696 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-4696 [HIGH] CVE-2026-4696 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4696 :
NixOS vulnerability analysis and mitigation
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, 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) 7.5
Exploitation Probability (EPSS) N/A
Affected packages and libraries
rhel10::thunderbird-flatpak.src
MozillaFirefox-branding-upstream
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Mar 31, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Mar 31, 2026
Cha
Bugzilla
CVE-2026-4696 firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component
bugzilla·2026-03-24·CVSS 9.8
CVE-2026-4696 [CRITICAL] CVE-2026-4696 firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component
CVE-2026-4696 firefox: thunderbird: Use-after-free in the Layout: Text and Fonts component
Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, 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 Enter
https://bugzilla.mozilla.org/show_bug.cgi?id=2020190https://www.mozilla.org/security/advisories/mfsa2026-20/https://www.mozilla.org/security/advisories/mfsa2026-21/https://www.mozilla.org/security/advisories/mfsa2026-22/https://www.mozilla.org/security/advisories/mfsa2026-23/https://www.mozilla.org/security/advisories/mfsa2026-24/https://access.redhat.com/errata/RHSA-2026:5930https://access.redhat.com/errata/RHSA-2026:5931https://access.redhat.com/errata/RHSA-2026:5932https://access.redhat.com/errata/RHSA-2026:6188https://access.redhat.com/errata/RHSA-2026:6342https://access.redhat.com/errata/RHSA-2026:6917https://access.redhat.com/errata/RHSA-2026:7837https://access.redhat.com/errata/RHSA-2026:7838https://access.redhat.com/errata/RHSA-2026:7839https://access.redhat.com/errata/RHSA-2026:7840https://access.redhat.com/errata/RHSA-2026:7841https://access.redhat.com/errata/RHSA-2026:7842https://access.redhat.com/errata/RHSA-2026:7843https://access.redhat.com/errata/RHSA-2026:7845https://access.redhat.com/errata/RHSA-2026:7858https://access.redhat.com/errata/RHSA-2026:8284https://access.redhat.com/errata/RHSA-2026:8285https://access.redhat.com/errata/RHSA-2026:8286https://access.redhat.com/errata/RHSA-2026:8287https://access.redhat.com/errata/RHSA-2026:8288https://access.redhat.com/errata/RHSA-2026:8289https://access.redhat.com/errata/RHSA-2026:8290https://access.redhat.com/errata/RHSA-2026:8315https://access.redhat.com/errata/RHSA-2026:8427https://access.redhat.com/errata/RHSA-2026:8850https://access.redhat.com/security/cve/CVE-2026-4696https://bugzilla.redhat.com/show_bug.cgi?id=2450740https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4696.json
2026-03-24
Published