CVE-2026-2763
published 2026-02-24CVE-2026-2763: Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and…
PriorityP350critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.47%
37.6th percentile
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Affected
13 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| debian | firefox-esr | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| debian | thunderbird | < firefox 148.0-1 (sid) | firefox 148.0-1 (sid) |
| mozilla | firefox | < 115.33.0 | 115.33.0 |
| mozilla | firefox | < 148.0 | 148.0 |
| mozilla | firefox | — | — |
| mozilla | firefox | >= 128.0 < 140.8.0 | 140.8.0 |
| mozilla | thunderbird | < 140.8.0 | 140.8.0 |
| mozilla | thunderbird | < 148.0 | 148.0 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb11u1 | 1:140.8.0esr-1~deb11u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb12u1 | 1:140.8.0esr-1~deb12u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1~deb13u1 | 1:140.8.0esr-1~deb13u1 |
| mozilla | thunderbird | >= 0 < 1:140.8.0esr-1 | 1:140.8.0esr-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 JavaScript Engine component
vendor_redhat·2026-02-24·CVSS 9.8
CVE-2026-2763 [CRITICAL] firefox: thunderbird: Use-after-free in the JavaScript Engine component
firefox: thunderbird: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
A flaw was found in Firefox and Thunderbird. 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: 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
Debian
CVE-2026-2763: firefox - Use-after-free in the JavaScript Engine component. This vulnerability affects Fi...
vendor_debian·2026·CVSS 9.8
CVE-2026-2763 [CRITICAL] CVE-2026-2763: 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 < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Scope: local
sid: resolved (fixed in 148.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-15: CVE-2026-2763
vendor_mozilla·CVSS 9.8
CVE-2026-2763 [CRITICAL] Mozilla Foundation Security Advisory 2026-15: CVE-2026-2763
Mozilla Foundation Security Advisory 2026-15
CVE: CVE-2026-2763
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.8
Mozilla
Mozilla Foundation Security Advisory 2026-16: CVE-2026-2763
vendor_mozilla·CVSS 9.8
CVE-2026-2763 [CRITICAL] Mozilla Foundation Security Advisory 2026-16: CVE-2026-2763
Mozilla Foundation Security Advisory 2026-16
CVE: CVE-2026-2763
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 148
Mozilla
Mozilla Foundation Security Advisory 2026-14: CVE-2026-2763
vendor_mozilla·CVSS 9.8
CVE-2026-2763 [CRITICAL] Mozilla Foundation Security Advisory 2026-14: CVE-2026-2763
Mozilla Foundation Security Advisory 2026-14
CVE: CVE-2026-2763
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 115.33
Mozilla
Mozilla Foundation Security Advisory 2026-13: CVE-2026-2763
vendor_mozilla·CVSS 9.8
CVE-2026-2763 [CRITICAL] Mozilla Foundation Security Advisory 2026-13: CVE-2026-2763
Mozilla Foundation Security Advisory 2026-13
CVE: CVE-2026-2763
Product: Firefox
Impact: high
Fixed in: Firefox 148
Mozilla
Mozilla Foundation Security Advisory 2026-17: CVE-2026-2763
vendor_mozilla·CVSS 9.8
CVE-2026-2763 [CRITICAL] Mozilla Foundation Security Advisory 2026-17: CVE-2026-2763
Mozilla Foundation Security Advisory 2026-17
CVE: CVE-2026-2763
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.8
GHSA
GHSA-qmr7-46p8-4c5r: Use-after-free in the JavaScript Engine component
ghsa_unreviewed·2026-02-24
CVE-2026-2763 [CRITICAL] CWE-416 GHSA-qmr7-46p8-4c5r: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, and Firefox ESR < 140.8.
OSV
CVE-2026-2763: Use-after-free in the JavaScript Engine component
osv·2026-02-24·CVSS 9.8
CVE-2026-2763 [CRITICAL] CVE-2026-2763: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-2763 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 9.8
CVE-2026-2763 [CRITICAL] CVE-2026-2763 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-2763 :
NixOS vulnerability analysis and mitigation
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and Thunderbird < 140.8.
Source : NVD
## 9.8
Score
Published February 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) 6.2
Exploitation Probability (EPSS) N/A
Affected packages and libraries
thunderbird
firefox-x11
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Mar 03, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Mar 02, 2026
Debian 11, 12, 13, 14 Severity CRITICAL Has Fi
Bugzilla
CVE-2026-2763 firefox: thunderbird: Use-after-free in the JavaScript Engine component
bugzilla·2026-02-24·CVSS 9.8
CVE-2026-2763 [CRITICAL] CVE-2026-2763 firefox: thunderbird: Use-after-free in the JavaScript Engine component
CVE-2026-2763 firefox: thunderbird: Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability affects Firefox < 148, Firefox ESR < 115.33, and Firefox ESR < 140.8.
Discussion:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2026:3338 https://access.redhat.com/errata/RHSA-2026:3338
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2026:3339 https://access.redhat.com/errata/RHSA-2026:3339
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:3361 https://access.redhat.com/errata/RHSA-2026:3361
---
This issue has been addressed in the following products:
Red Hat Enterprise Linu
https://bugzilla.mozilla.org/show_bug.cgi?id=2012018https://www.mozilla.org/security/advisories/mfsa2026-13/https://www.mozilla.org/security/advisories/mfsa2026-14/https://www.mozilla.org/security/advisories/mfsa2026-15/https://www.mozilla.org/security/advisories/mfsa2026-16/https://www.mozilla.org/security/advisories/mfsa2026-17/https://access.redhat.com/errata/RHSA-2026:3338https://access.redhat.com/errata/RHSA-2026:3339https://access.redhat.com/errata/RHSA-2026:3361https://access.redhat.com/errata/RHSA-2026:3491https://access.redhat.com/errata/RHSA-2026:3492https://access.redhat.com/errata/RHSA-2026:3493https://access.redhat.com/errata/RHSA-2026:3494https://access.redhat.com/errata/RHSA-2026:3495https://access.redhat.com/errata/RHSA-2026:3496https://access.redhat.com/errata/RHSA-2026:3497https://access.redhat.com/errata/RHSA-2026:3515https://access.redhat.com/errata/RHSA-2026:3516https://access.redhat.com/errata/RHSA-2026:3517https://access.redhat.com/errata/RHSA-2026:3976https://access.redhat.com/errata/RHSA-2026:3978https://access.redhat.com/errata/RHSA-2026:3979https://access.redhat.com/errata/RHSA-2026:3980https://access.redhat.com/errata/RHSA-2026:3981https://access.redhat.com/errata/RHSA-2026:3982https://access.redhat.com/errata/RHSA-2026:3983https://access.redhat.com/errata/RHSA-2026:3984https://access.redhat.com/errata/RHSA-2026:4022https://access.redhat.com/errata/RHSA-2026:4152https://access.redhat.com/errata/RHSA-2026:4260https://access.redhat.com/errata/RHSA-2026:4432https://access.redhat.com/security/cve/CVE-2026-2763https://bugzilla.redhat.com/show_bug.cgi?id=2442316https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2763.json
2026-02-24
Published