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Fencer Vulns
critical 9.8

CVE-2026-84140 json

Site isolation issue in the DOM: Navigation component

published 2026-09-01 2 mo ago modified 2026-09-03 2 mo ago also EUVD-2026-69088

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 7%
public exploits
0
none known

Summary

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

Patch / fix

  • mozilla firefox 153.2.0, 155.0.0
  • mozilla thunderbird 153.2.0, 155.0
  • MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7 153.2.0-150400.13.3.1
  • MozillaFirefox SLES for SAP applications 16.0, SLES 16.0 153.2.0-160000.1.1
  • mozilla-nss SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 3.125-150400.3.74.1
  • mozilla-nspr SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 4.39-150400.12.3.1
  • MozillaFirefox SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 153.2.0-150400.157.5.1
  • MozillaFirefox-branding-SLE SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 153-150400.14.3.1
  • mozilla-nss SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 3.125-58.147.1
  • mozilla-nspr SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 4.39-19.39.1

suse advisories SUSE-SU-2026:4268-1SUSE-SU-2026:23784-1SUSE-SU-2026:4156-1SUSE-SU-2026:4140-1

  • MozillaThunderbird openSUSE Tumbleweed 153.4.0-1.1
  • MozillaFirefox openSUSE Leap 16.0 153.2.0-160000.1.1
  • MozillaFirefox openSUSE Tumbleweed 155.0-1.1
  • firefox-esr openSUSE Tumbleweed 153.2.0-1.1

opensuse advisories openSUSE-SU-2026:12098-1openSUSE-SU-2026:21853-1openSUSE-SU-2026:11677-1openSUSE-SU-2026:11666-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-84140 updated cvss 3.4

firefox: thunderbird: Site isolation issue in the DOM: Navigation component

  • Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 firefox, thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird Red Hat Enterprise Linux 9 firefox, firefox-x11, thunderbird Red Hat Enterprise Linux 10 firefox, thunderbird, rhel10/firefox-flatpak, rhel10/thunderbird-flatpak
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
2 mo ago

Exploit prediction

0.18% chance of exploitation in the next 30 days, higher than 7% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Mozilla Firefox
  • Mozilla Thunderbird

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.