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CVE-2026-84143

Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15

Published: Sep 1, 2026Updated: Sep 3, 2026 Sources: CVE List NVDCWE-119
9.8CRITICAL
NVD MITRE
EPSS Score
0.4%
Top 69.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

Description

Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-119CWE-200

Affected Products

Mozilla
oss-project·USaka mozilla corp.
FirefoxOn-premDesktop App
Consumer Software / browser
ThunderbirdOn-premDesktop App
Communications / email-server-client
and 2 more affected products View all →

Exploitability

Official Patch Available
Is your org exposed to CVE-2026-84143?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes for MITRE ATT&CK details · drag to pan · Ctrl/⌘ + scroll to zoom, or go fullscreen.

MITRE ATT&CK

3 techniques
Collection
Initial Access
Privilege Escalation
View detailed technique mapping

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048793%2C2054645%2C2057114%2C2059109%2C2061287
bugzilla.mozilla.org
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2054631%2C2054657%2C2055007%2C2055681%2C2057107%2C2058087%2C2058088%2C2058090%2C2058095%2C2058101%2C2059183%2C2059185%2C2061301%2C2061325
bugzilla.mozilla.org
https://bugzilla.mozilla.org/show_bug.cgi?id=2057108
bugzilla.mozilla.org
and 6 more references View all →

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