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CVE-2026-0891

32
FAUCET Score

CVE-2026-0891 details memory safety bugs in Mozilla Firefox and Thunderbird, specifically affecting versions prior to Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7. Rated 8.1 HIGH (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H), this vulnerability could lead to arbitrary code execution with sufficient effort, despite its high attack complexity. While no public exploit code exists (Metasploit, Nuclei, ExploitDB), it has garnered significant community discussion and media coverage, including mentions of active exploitation in a January 2026 Microsoft Patch Tuesday article.

Impacted Technologies

VendorProductVersion(s)CPE
< 140.7.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
< 147.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
< 140.7.0CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*
< 147.0CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.41%
Probability of exploitation in next 30 days
EPSS Percentile
33.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0041 is in the 9th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (36)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: firefox-0:140.7.0-1.el10_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: thunderbird-0:140.7.0-1.el10_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 10.0 Extended Update SupportFixed in: firefox-0:140.7.0-1.el10_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 10.0 Extended Update SupportFixed in: thunderbird-0:140.7.0-1.el10_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7 Extended Lifecycle SupportFixed in: firefox-0:140.7.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:140.7.0-1.el8_10
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:140.7.0-1.el8_10
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: thunderbird-0:140.7.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Advanced Update SupportFixed in: firefox-0:140.7.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: thunderbird-0:140.7.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportFixed in: firefox-0:140.7.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnFixed in: thunderbird-0:140.7.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnFixed in: firefox-0:140.7.0-1.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportFixed in: thunderbird-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportFixed in: firefox-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Telecommunications Update ServiceFixed in: thunderbird-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Telecommunications Update ServiceFixed in: firefox-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Update Services for SAP SolutionsFixed in: thunderbird-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.6 Update Services for SAP SolutionsFixed in: firefox-0:140.7.0-1.el8_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceFixed in: thunderbird-0:140.7.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceFixed in: firefox-0:140.7.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsFixed in: thunderbird-0:140.7.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsFixed in: firefox-0:140.7.0-1.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: firefox-0:140.7.0-1.el9_7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: thunderbird-0:140.7.0-1.el9_7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.0 Update Services for SAP SolutionsFixed in: thunderbird-0:140.7.0-1.el9_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.0 Update Services for SAP SolutionsFixed in: firefox-0:140.7.0-1.el9_0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsFixed in: thunderbird-0:140.7.0-1.el9_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsFixed in: firefox-0:140.7.0-1.el9_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.4 Extended Update SupportFixed in: thunderbird-0:140.7.0-1.el9_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.4 Extended Update SupportFixed in: firefox-0:140.7.0-1.el9_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.6 Extended Update SupportFixed in: thunderbird-0:140.7.0-2.el9_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.6 Extended Update SupportFixed in: firefox-0:140.7.0-1.el9_6
View patch
mozillavendor investigatingvia nvd_reference
View patch
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: rhel10/firefox-flatpak
redhatno patchvia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: rhel10/thunderbird-flatpak

Vendor Advisories (1)

redhatCVE-2026-0891Important

firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147

Jan 13, 2026

References

access.redhat.com / errata/RHSA-2026:0667
access.redhat.com / errata/RHSA-2026:0694
access.redhat.com / errata/RHSA-2026:0924
access.redhat.com / errata/RHSA-2026:1320
access.redhat.com / errata/RHSA-2026:1413
access.redhat.com / errata/RHSA-2026:1414
access.redhat.com / errata/RHSA-2026:1415
access.redhat.com / errata/RHSA-2026:1461
access.redhat.com / errata/RHSA-2026:1462
access.redhat.com / errata/RHSA-2026:1471
access.redhat.com / errata/RHSA-2026:1487
access.redhat.com / errata/RHSA-2026:2041
access.redhat.com / errata/RHSA-2026:2043
access.redhat.com / errata/RHSA-2026:2044
access.redhat.com / errata/RHSA-2026:2047
access.redhat.com / errata/RHSA-2026:2069
access.redhat.com / errata/RHSA-2026:2070
access.redhat.com / errata/RHSA-2026:2073
access.redhat.com / errata/RHSA-2026:2074
access.redhat.com / errata/RHSA-2026:2220
access.redhat.com / errata/RHSA-2026:2231
access.redhat.com / errata/RHSA-2026:2271
access.redhat.com / errata/RHSA-2026:2286
access.redhat.com / security/cve/CVE-2026-0891
bugzilla.redhat.com / show_bug.cgi
security.access.redhat.com / data/csaf/v2/vex/2026/cve-2026-0891.json
bugzilla.mozilla.org / buglist.cgi
Broken Link
mozilla.org / security/advisories/mfsa2026-01
Vendor Advisory
mozilla.org / security/advisories/mfsa2026-03
Vendor Advisory
mozilla.org / security/advisories/mfsa2026-04
Vendor Advisory
mozilla.org / security/advisories/mfsa2026-05
Vendor Advisory