CVE-2026-4717
published 2026-03-24CVE-2026-4717: Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
PriorityP352critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.42%
34.2th percentile
Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected
10 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 | < 140.9.0 | 140.9.0 |
| mozilla | firefox | < 149.0 | 149.0 |
| mozilla | firefox | — | — |
| 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: Privilege escalation in the Netmonitor component
vendor_redhat·2026-03-24·CVSS 9.8
CVE-2026-4717 [CRITICAL] CWE-266 firefox: thunderbird: Privilege escalation in the Netmonitor component
firefox: thunderbird: Privilege escalation in the Netmonitor component
Privilege escalation in the Netmonitor 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:
Privilege escalation in the Netmonitor 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) -
Debian
CVE-2026-4717: firefox - Privilege escalation in the Netmonitor component. This vulnerability affects Fir...
vendor_debian·2026·CVSS 9.8
CVE-2026-4717 [CRITICAL] CVE-2026-4717: firefox - Privilege escalation in the Netmonitor component. This vulnerability affects Fir...
Privilege escalation in the Netmonitor component. This vulnerability affects Firefox < 149, 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-2026-4717
vendor_mozilla·CVSS 9.8
CVE-2026-4717 [CRITICAL] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4717
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4717
Product: Firefox
Impact: high
Fixed in: Firefox 149
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4717
vendor_mozilla·CVSS 9.8
CVE-2026-4717 [CRITICAL] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4717
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4717
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4717
vendor_mozilla·CVSS 9.8
CVE-2026-4717 [CRITICAL] Mozilla Foundation Security Advisory 2026-24: CVE-2026-4717
Mozilla Foundation Security Advisory 2026-24
CVE: CVE-2026-4717
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4717
vendor_mozilla·CVSS 9.8
CVE-2026-4717 [CRITICAL] Mozilla Foundation Security Advisory 2026-22: CVE-2026-4717
Mozilla Foundation Security Advisory 2026-22
CVE: CVE-2026-4717
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.9
OSV
CVE-2026-4717: Privilege escalation in the Netmonitor component
osv·2026-03-24·CVSS 9.8
CVE-2026-4717 [CRITICAL] CVE-2026-4717: Privilege escalation in the Netmonitor component
Privilege escalation in the Netmonitor component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
GHSA
GHSA-pqfx-cwf8-965q: Privilege escalation in the Netmonitor component
ghsa_unreviewed·2026-03-24
CVE-2026-4717 [CRITICAL] GHSA-pqfx-cwf8-965q: Privilege escalation in the Netmonitor component
Privilege escalation in the Netmonitor component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-4717 firefox: thunderbird: Privilege escalation in the Netmonitor component
bugzilla·2026-03-24·CVSS 9.8
CVE-2026-4717 [CRITICAL] CVE-2026-4717 firefox: thunderbird: Privilege escalation in the Netmonitor component
CVE-2026-4717 firefox: thunderbird: Privilege escalation in the Netmonitor component
Privilege escalation in the Netmonitor 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 h
Wiz
CVE-2026-4717 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-4717 [HIGH] CVE-2026-4717 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4717 :
NixOS vulnerability analysis and mitigation
Privilege escalation in the Netmonitor 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
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
firefox
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
Deb
2026-03-24
Published