Internally found bugs fixed in Thunderbird 155 and Thunderbird ESR 153.2

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-84144
StatePUBLISHED
Assignermozilla
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-01 13:20:08 UTC
Updated2026-09-03 16:33:15 UTC
DescriptionInternally found bugs present in Thunderbird 154 and Thunderbird ESR 153.1. 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 153.2, Thunderbird 155, and Thunderbird 153.2.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

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

EPSS: 0.002410000 probability, percentile 0.151460000 (date 2026-09-04)

Problem Types: CWE-119 | CWE-119 CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Mozilla Firefox All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mozilla Firefox unaffected 153.2 153.* rpm Not specified
CNA Mozilla Firefox unaffected 155 * rpm Not specified
CNA Mozilla Thunderbird unaffected 153.2 153.* rpm Not specified
CNA Mozilla Thunderbird unaffected 155 * rpm Not specified

References

ReferenceSourceLinkTags
bugzilla.mozilla.org/buglist.cgi [email protected] bugzilla.mozilla.org Broken Link
bugzilla.mozilla.org/buglist.cgi [email protected] bugzilla.mozilla.org Broken Link
www.mozilla.org/security/advisories/mfsa2026-88 [email protected] www.mozilla.org Vendor Advisory
www.mozilla.org/security/advisories/mfsa2026-85 [email protected] www.mozilla.org Vendor Advisory
www.mozilla.org/security/advisories/mfsa2026-86 [email protected] www.mozilla.org Vendor Advisory
www.mozilla.org/security/advisories/mfsa2026-82 [email protected] www.mozilla.org Vendor Advisory
bugzilla.mozilla.org/buglist.cgi [email protected] bugzilla.mozilla.org Broken Link
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Leo Tenenbaum, Tom Ritter and the Mozilla Fuzzing Team (en)

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