Privilege escalation in WebExtensions
Published Jul 21, 2026
8.8
HIGHCVSS 3.1
EPSS 0.24%
Description
Privilege escalation in WebExtensions. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.
Affected products
No data.
- < 140.13.0
- < 153.0.0
- < 140.13.0
- ≥ 141.0 · < 153.0
No data.
Red Hat Enterprise Linux 10
firefox-0:140.13.0-1.el10_2
Fixed · RHSA-2026:47101
Red Hat Enterprise Linux 10
thunderbird-0:140.13.0-1.el10_2
Fixed · RHSA-2026:49621
Red Hat Enterprise Linux 10.0 Extended Update Support
firefox-0:140.13.0-1.el10_0
Fixed · RHSA-2026:54181
Red Hat Enterprise Linux 10.0 Extended Update Support
thunderbird-0:140.13.0-1.el10_0
Fixed · RHSA-2026:53445
Red Hat Enterprise Linux 7 Extended Lifecycle Support
firefox-0:140.13.0-1.el7_9
Fixed · RHSA-2026:54248
Red Hat Enterprise Linux 8
firefox-0:140.13.0-1.el8_10
Fixed · RHSA-2026:47105
Red Hat Enterprise Linux 8
thunderbird-0:140.13.0-1.el8_10
Fixed · RHSA-2026:49922
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
firefox-0:140.13.0-1.el8_4
Fixed · RHSA-2026:54180
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
thunderbird-0:140.13.0-1.el8_4
Fixed · RHSA-2026:53455
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
firefox-0:140.13.0-1.el8_4
Fixed · RHSA-2026:54180
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
thunderbird-0:140.13.0-1.el8_4
Fixed · RHSA-2026:53455
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
firefox-0:140.13.0-1.el8_6
Fixed · RHSA-2026:54259
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
thunderbird-0:140.13.0-1.el8_6
Fixed · RHSA-2026:53453
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
firefox-0:140.13.0-1.el8_6
Fixed · RHSA-2026:54259
Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On
thunderbird-0:140.13.0-1.el8_6
Fixed · RHSA-2026:53453
Red Hat Enterprise Linux 8.8 Telecommunications Update Service
firefox-0:140.13.0-1.el8_8
Fixed · RHSA-2026:54339
Red Hat Enterprise Linux 8.8 Telecommunications Update Service
thunderbird-0:140.13.0-1.el8_8
Fixed · RHSA-2026:53454
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
firefox-0:140.13.0-1.el8_8
Fixed · RHSA-2026:54339
Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
thunderbird-0:140.13.0-1.el8_8
Fixed · RHSA-2026:53454
Red Hat Enterprise Linux 9
firefox-0:140.13.0-1.el9_8
Fixed · RHSA-2026:47104
Red Hat Enterprise Linux 9
thunderbird-0:140.13.0-1.el9_8
Fixed · RHSA-2026:49921
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
firefox-0:140.13.0-1.el9_2
Fixed · RHSA-2026:54185
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
thunderbird-0:140.13.0-1.el9_2
Fixed · RHSA-2026:53475
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
firefox-0:140.13.0-1.el9_4
Fixed · RHSA-2026:54182
Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
thunderbird-0:140.13.0-1.el9_4
Fixed · RHSA-2026:53444
Red Hat Enterprise Linux 9.6 Extended Update Support
firefox-0:140.13.0-1.el9_6
Fixed · RHSA-2026:54249
Red Hat Enterprise Linux 9.6 Extended Update Support
thunderbird-0:140.13.0-1.el9_6
Fixed · RHSA-2026:53446
Red Hat Enterprise Linux 10
rhel10/firefox-flatpak
Affected
Red Hat Enterprise Linux 10
rhel10/thunderbird-flatpak
Affected
Red Hat Enterprise Linux 6
firefox
Out of support scope
Red Hat Enterprise Linux 6
thunderbird
Out of support scope
Red Hat Enterprise Linux 7
thunderbird
Out of support scope
| Product | Package | State | Advisory |
|---|---|---|---|
| Red Hat Enterprise Linux 10 | firefox-0:140.13.0-1.el10_2 | Fixed | RHSA-2026:47101 |
| Red Hat Enterprise Linux 10 | thunderbird-0:140.13.0-1.el10_2 | Fixed | RHSA-2026:49621 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | firefox-0:140.13.0-1.el10_0 | Fixed | RHSA-2026:54181 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | thunderbird-0:140.13.0-1.el10_0 | Fixed | RHSA-2026:53445 |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | firefox-0:140.13.0-1.el7_9 | Fixed | RHSA-2026:54248 |
| Red Hat Enterprise Linux 8 | firefox-0:140.13.0-1.el8_10 | Fixed | RHSA-2026:47105 |
| Red Hat Enterprise Linux 8 | thunderbird-0:140.13.0-1.el8_10 | Fixed | RHSA-2026:49922 |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | firefox-0:140.13.0-1.el8_4 | Fixed | RHSA-2026:54180 |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | thunderbird-0:140.13.0-1.el8_4 | Fixed | RHSA-2026:53455 |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | firefox-0:140.13.0-1.el8_4 | Fixed | RHSA-2026:54180 |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | thunderbird-0:140.13.0-1.el8_4 | Fixed | RHSA-2026:53455 |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | firefox-0:140.13.0-1.el8_6 | Fixed | RHSA-2026:54259 |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | thunderbird-0:140.13.0-1.el8_6 | Fixed | RHSA-2026:53453 |
| Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On | firefox-0:140.13.0-1.el8_6 | Fixed | RHSA-2026:54259 |
| Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On | thunderbird-0:140.13.0-1.el8_6 | Fixed | RHSA-2026:53453 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | firefox-0:140.13.0-1.el8_8 | Fixed | RHSA-2026:54339 |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | thunderbird-0:140.13.0-1.el8_8 | Fixed | RHSA-2026:53454 |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | firefox-0:140.13.0-1.el8_8 | Fixed | RHSA-2026:54339 |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | thunderbird-0:140.13.0-1.el8_8 | Fixed | RHSA-2026:53454 |
| Red Hat Enterprise Linux 9 | firefox-0:140.13.0-1.el9_8 | Fixed | RHSA-2026:47104 |
| Red Hat Enterprise Linux 9 | thunderbird-0:140.13.0-1.el9_8 | Fixed | RHSA-2026:49921 |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | firefox-0:140.13.0-1.el9_2 | Fixed | RHSA-2026:54185 |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | thunderbird-0:140.13.0-1.el9_2 | Fixed | RHSA-2026:53475 |
| Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions | firefox-0:140.13.0-1.el9_4 | Fixed | RHSA-2026:54182 |
| Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions | thunderbird-0:140.13.0-1.el9_4 | Fixed | RHSA-2026:53444 |
| Red Hat Enterprise Linux 9.6 Extended Update Support | firefox-0:140.13.0-1.el9_6 | Fixed | RHSA-2026:54249 |
| Red Hat Enterprise Linux 9.6 Extended Update Support | thunderbird-0:140.13.0-1.el9_6 | Fixed | RHSA-2026:53446 |
| Red Hat Enterprise Linux 10 | rhel10/firefox-flatpak | Affected | n/a |
| Red Hat Enterprise Linux 10 | rhel10/thunderbird-flatpak | Affected | n/a |
| Red Hat Enterprise Linux 6 | firefox | Out of support scope | n/a |
| Red Hat Enterprise Linux 6 | thunderbird | Out of support scope | n/a |
| Red Hat Enterprise Linux 7 | thunderbird | Out of support scope | n/a |
No package ranges for this CVE.
Remediation
Red Hat statement
Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Metrics
No CVSS v4.0 score for this CVE.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
1 other source (Red Hat) ▾
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
NoneAutomatable
NoTechnical Impact
TotalDecision
n/aAssessed Jul 24, 2026 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
Jul–Oct 2026- EPSS v5
Percentile over time
- EPSS v5
Table of values (2 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 0.24% (0.00241) | 13.74th | v5 (v2026.06.15) |
| Jul 22, 2026 | 0.14% (0.00142) | 3.94th | v5 (v2026.06.15) |
References (11)
- https://access.redhat.com/security/cve/CVE-2026-16396 Vendor Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=2047240 Permissions Required
- https://bugzilla.redhat.com/show_bug.cgi?id=2503521 Issue Tracking
- https://nvd.nist.gov/vuln/detail/CVE-2026-16396
- https://www.cve.org/CVERecord?id=CVE-2026-16396
- https://www.mozilla.org/security/advisories/mfsa2026-68/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-70/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-70/#CVE-2026-16396
- https://www.mozilla.org/security/advisories/mfsa2026-71/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-72/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-72/#CVE-2026-16396
Change history (0)
No recorded changes yet.