Memory safety bugs fixed in Firefox 140 and Thunderbird 140

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-6436
StatePUBLISHED
Assignermozilla
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-06-24 13:15:24 UTC
Updated2026-04-13 15:17:08 UTC
DescriptionMemory safety bugs present in Firefox 139 and Thunderbird 139. 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 140 and Thunderbird 140.

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from ADP

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

EPSS: 0.001410000 probability, percentile 0.342880000 (date 2026-04-15)

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

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary8.1HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Mozilla Firefox All All All All
Application Mozilla Thunderbird All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mozilla Firefox unaffected 140 * rpm Not specified
CNA Mozilla Thunderbird unaffected 140 * rpm Not specified

References

ReferenceSourceLinkTags
www.mozilla.org/security/advisories/mfsa2025-51 [email protected] www.mozilla.org Vendor Advisory
www.mozilla.org/security/advisories/mfsa2025-54 [email protected] www.mozilla.org Vendor Advisory
bugzilla.mozilla.org/buglist.cgi [email protected] bugzilla.mozilla.org Permissions Required
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: Andrew McCreight, Gabriele Svelto, Beth Rennie (she/her), Steven Michaud, the Mozilla Fuzzing Team (en)

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