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

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Summary

CVECVE-2026-6786
StatePUBLISHED
Assignermozilla
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-26 19:53:39 UTC
Updated2026-04-26 19:53:39 UTC
DescriptionMemory 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.

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: 0.000460000 probability, percentile 0.140870000 (date 2026-04-26)

Problem Types: CWE-125 | CWE-416 | CWE-787 | CWE-416 CWE-416 Use After Free | CWE-125 CWE-125 Out-of-bounds Read | CWE-787 CWE-787 Out-of-bounds Write

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mozilla Firefox unaffected 140.10 140.* rpm Not specified
CNA Mozilla Firefox unaffected 150 * rpm Not specified
CNA Mozilla Thunderbird unaffected 140.10 140.* rpm Not specified
CNA Mozilla Thunderbird unaffected 150 * rpm Not specified

References

ReferenceSourceLinkTags
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2010727%2C2019004%2C2019224%2C2019547%2C2020378%2C2022381%2C2022608%2C2022785%2C2023120%2C2023128%2C2023140%2C2023279%2C2023836%2C2023882%2C2023925%2C2023950%2C2023959%2C2023965%2C2024243%2C2024245%2C2024247%2C2024253%2C2024346%2C2024357%2C2024416%2C2024420%2C2024429%2C2024432%2C2024455%2C2024466%2C2024468%2C2024476%2C2024664%2C2024666%2C2024669%2C2024670%2C2024671%2C2024761%2C2024918%2C2025292%2C2025332%2C2025348%2C2025384%2C2025395%2C2025458%2C2025461%2C2025463%2C2025481%2C2025483%2C2025485%2C2025494%2C2025506%2C2025511%2C2025513%2C2025520%2C2026277%2C2026282%2C2026288%2C2026289%2C2026311%2C2026312%2C2026869%2C2027152%2C2027161%2C2027238%2C2027261%2C2027269%2C2027274%2C2027280%2C2027281%2C2027300%2C2027302%2C2027331%2C2027339%2C2027340%2C2027738%2C2027975%2C2028000%2C2028011%2C2028289%2C2028525%2C2028728%2C2028887%2C2028888%2C2028896%2C2029063%2C2029064%2C2029290%2C2029291%2C2029294%2C2029300%2C2029304%2C2029316%2C2029317%2C2029401%2C20 [email protected] bugzilla.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-34 [email protected] www.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-30 [email protected] www.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-32 [email protected] www.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-33 [email protected] www.mozilla.org
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2010727%2C2019004%2C2019224%2C2019547%2C2020378%2C2022381%2C2022608%2C2022785%2C2023120%2C2023128%2C2023140%2C2023279%2C2023836%2C2023882%2C2023925%2C2023950%2C2023959%2C2023965%2C2024243%2C2024245%2C2024247%2C2024253%2C2024346%2C2024357%2C2024416%2C2024420%2C2024429%2C2024432%2C2024455%2C2024466%2C2024468%2C2024476%2C2024664%2C2024666%2C2024669%2C2024670%2C2024671%2C2024761%2C2024918%2C2025292%2C2025332%2C2025348%2C2025384%2C2025395%2C2025458%2C2025461%2C2025463%2C2025481%2C2025483%2C2025485%2C2025494%2C2025506%2C2025511%2C2025513%2C2025520%2C2026277%2C2026282%2C2026288%2C2026289%2C2026311%2C2026312%2C2026869%2C2027152%2C2027161%2C2027238%2C2027261%2C2027269%2C2027274%2C2027280%2C2027281%2C2027300%2C2027302%2C2027331%2C2027339%2C2027340%2C2027738%2C2027975%2C2028000%2C2028011%2C2028289%2C2028525%2C2028728%2C2028887%2C2028888%2C2028896%2C2029063%2C2029064%2C2029290%2C2029291%2C2029294%2C2029300%2C2029304%2C2029316%2C2029317%2C2029401%2C20 MITRE bugzilla.mozilla.org
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: Alex Franchuk, Andrew McCreight, Brian Grinstead, Christian Holler, Jan de Mooij, Maurice Dauer, Sebastian Hengst, Tom Schuster and the Mozilla Fuzzing Team (en)

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