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Fencer Vulns
high 7.5

CVE-2026-6786 json

Memory safety bugs fixed in Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150

published 2026-04-21 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-24127

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits
0
none known

Summary

Memory safety bugs present in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 0:140.10.0-1.el10_1, 0:140.10.0-1.el10_2
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:140.10.0-1.el10_0
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:140.10.0-2.el7_9
  • Red Hat Red Hat Enterprise Linux 8 0:140.10.0-1.el8_10
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support 0:140.10.0-1.el8_4
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On 0:140.10.0-1.el8_4
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support 0:140.10.0-1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service 0:140.10.0-1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions 0:140.10.0-1.el8_6
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service 0:140.10.0-1.el8_8
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions 0:140.10.0-1.el8_8
  • Red Hat Red Hat Enterprise Linux 9 0:140.10.0-1.el9_7, 0:140.10.0-1.el9_8, 0:140.10.1-1.el9_8
  • Red Hat Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions 0:140.10.0-1.el9_0
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:140.10.0-1.el9_2
  • Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support 0:140.10.0-1.el9_4
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:140.10.0-1.el9_6
  • firefox-esr Debian 12 140.10.0esr-1~deb12u1
  • firefox-esr Debian 13 140.10.0esr-1~deb13u1
  • firefox-esr Debian 14 140.10.0esr-1
  • thunderbird Debian 12 1:140.10.0esr-1~deb12u1
  • thunderbird Debian 13 1:140.10.0esr-1~deb13u1
  • thunderbird Debian 14 1:140.10.0esr-1

debian advisories DEBIAN-CVE-2026-6786

  • thunderbird RHEL 9 140.10.1-1.el9_8
  • firefox RHEL 9 140.10.0-1.el9_8
  • firefox-x11 RHEL 9 140.10.0-1.el9_8
  • thunderbird RHEL 10.2 140.10.0-1.el10_2
  • firefox RHEL 10.2 140.10.0-1.el10_2
  • thunderbird RHEL 9 140.10.0-1.el9_7
  • thunderbird RHEL 8 140.10.0-1.el8_10
  • thunderbird RHEL 10.1 140.10.0-1.el10_1

red hat advisories RHSA-2026:19704RHSA-2026:19655RHSA-2026:19542RHSA-2026:19469RHSA-2026:19467RHSA-2026:19468

  • firefox-esr openSUSE Tumbleweed 153.0-1.1
  • MozillaFirefox openSUSE Tumbleweed 150.0-1.1
  • MozillaThunderbird openSUSE Tumbleweed 140.9.1-1.1

opensuse advisories openSUSE-SU-2026:11373-1openSUSE-SU-2026:10626-1openSUSE-SU-2026:10610-1

  • thunderbird AlmaLinux 9 140.10.1-1.el9_8.alma.1
  • thunderbird AlmaLinux 9 140.10.0-1.el9_7.alma.1
  • thunderbird AlmaLinux 8 140.10.0-1.el8_10.alma.1
  • thunderbird AlmaLinux 10 140.10.0-1.el10_1.alma.1
  • firefox AlmaLinux 9 140.10.0-1.el9_7.alma.1
  • firefox-x11 AlmaLinux 9 140.10.0-1.el9_7.alma.1
  • firefox AlmaLinux 8 140.10.0-1.el8_10.alma.1
  • firefox AlmaLinux 10 140.10.0-1.el10_1

almalinux advisories ALSA-2026:19348ALSA-2026:15892ALSA-2026:13537ALSA-2026:12285ALSA-2026:10757ALSA-2026:10766

  • thunderbird Rocky Linux 9 140.10.1-1.el9_8
  • firefox Rocky Linux 9 140.10.0-1.el9_7
  • thunderbird Rocky Linux 9 140.10.0-1.el9_7
  • thunderbird Rocky Linux 10 140.10.0-1.el10_1
  • thunderbird Rocky Linux 8 140.10.0-1.el8_10
  • firefox Rocky Linux 8 140.10.0-1.el8_10
  • firefox Rocky Linux 10 140.10.0-1.el10_1

rocky linux advisories RLSA-2026:19348RLSA-2026:19201RLSA-2026:15892RLSA-2026:12285RLSA-2026:13537RLSA-2026:10766

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-2026-6786 updated cvss 7.5

firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150

  • Red Hat Enterprise Linux 6 firefox, thunderbird Red Hat Enterprise Linux 7 thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 10 rhel10/firefox-flatpak, rhel10/thunderbird-flatpak
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 140.10.0-1.el8_10, thunderbird 140.10.0-1.el8_10
    fixed: vendor fix RHSA-2026:10766
  • Red Hat Enterprise Linux AppStream (v. 9) firefox 140.10.0-1.el9_7, firefox 140.10.0-1.el9_8, firefox-x11 140.10.0-1.el9_7, firefox-x11 140.10.0-1.el9_8, thunderbird 140.10.0-1.el9_7, thunderbird 140.10.1-1.el9_8
    fixed: vendor fix RHSA-2026:10757
  • Red Hat Enterprise Linux AppStream (v. 10) firefox 140.10.0-1.el10_1, firefox 140.10.0-1.el10_2, thunderbird 140.10.0-1.el10_1, thunderbird 140.10.0-1.el10_2
    fixed: vendor fix RHSA-2026:10767
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) firefox 140.10.0-1.el8_4, thunderbird 140.10.0-1.el8_4
    fixed: vendor fix RHSA-2026:19655
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) firefox 140.10.0-1.el8_6, thunderbird 140.10.0-1.el8_6 Red Hat Enterprise Linux AppStream E4S (v.8.6) firefox 140.10.0-1.el8_6, thunderbird 140.10.0-1.el8_6
    fixed: vendor fix RHSA-2026:19542
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) firefox 140.10.0-1.el8_8, thunderbird 140.10.0-1.el8_8
    fixed: vendor fix RHSA-2026:17477
show 9 more
  • Red Hat Enterprise Linux AppStream E4S (v.9.0) firefox 140.10.0-1.el9_0, thunderbird 140.10.0-1.el9_0
    fixed: vendor fix RHSA-2026:17687
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) firefox 140.10.0-1.el9_2, firefox-x11 140.10.0-1.el9_2, thunderbird 140.10.0-1.el9_2
    fixed: vendor fix RHSA-2026:17689
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) firefox 140.10.0-1.el10_0, thunderbird 140.10.0-1.el10_0
    fixed: vendor fix RHSA-2026:17690
  • Red Hat Enterprise Linux AppStream EUS (v.9.4) firefox 140.10.0-1.el9_4, firefox-x11 140.10.0-1.el9_4, thunderbird 140.10.0-1.el9_4
    fixed: vendor fix RHSA-2026:19464
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) firefox 140.10.0-1.el9_6, firefox-x11 140.10.0-1.el9_6, thunderbird 140.10.0-1.el9_6
    fixed: vendor fix RHSA-2026:17688
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) firefox 140.10.0-1.el8_4, thunderbird 140.10.0-1.el8_4
    fixed: vendor fix RHSA-2026:19655
  • Red Hat Enterprise Linux AppStream TUS (v.8.6) firefox 140.10.0-1.el8_6, thunderbird 140.10.0-1.el8_6
    fixed: vendor fix RHSA-2026:19542
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) firefox 140.10.0-1.el8_8, thunderbird 140.10.0-1.el8_8
    fixed: vendor fix RHSA-2026:17477
  • Red Hat Enterprise Linux Server (v. 7 ELS) firefox 140.10.0-2.el7_9
    fixed: vendor fix RHSA-2026:19704

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
no
Technical impact
total
Assessed
6 mo ago

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

  • Mozilla Firefox
  • Mozilla Thunderbird
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On
  • Red Hat Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  • Red Hat Red Hat Enterprise Linux 8.6 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 8.8 Telecommunications Update Service
  • Red Hat Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.4 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7

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.