CVE-2026-74987: Internally found bugs fixed in Thunderbird ESR 140.14, Thunderbird ESR 153.1 and Thunderbird 154
Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. 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.
Other sources
Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. 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.
— Mozilla
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 140.14 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 154 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 153.1 - Upgrade
Upgrade
Firefoxto a version that resolves this vulnerability.Fixed in 154 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 140.14 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 153.1 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 154 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 140.14 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 153.1
Event History
Parent advisories
This vulnerability appears in the following advisories.
Peer vulnerabilities
Found alongside the following vulnerabilities.
- CVE-2026-74934
- CVE-2026-74935
- CVE-2026-74936
- CVE-2026-74939
- CVE-2026-74940
- CVE-2026-74941
- CVE-2026-74942
- CVE-2026-74943
- CVE-2026-74944
- CVE-2026-74945
- CVE-2026-74946
- CVE-2026-74948
- CVE-2026-74949
- CVE-2026-74953
- CVE-2026-74957
- CVE-2026-74959
- CVE-2026-74960
- CVE-2026-74962
- CVE-2026-74963
- CVE-2026-74964
- CVE-2026-74965
- CVE-2026-74967
- CVE-2026-74969
- CVE-2026-74971
- CVE-2026-74972
- CVE-2026-74973
- CVE-2026-74974
- CVE-2026-74976
- CVE-2026-74983
- CVE-2026-74987
- CVE-2026-74990
- CVE-2026-75874
- CVE-2026-74937
- CVE-2026-74938
- CVE-2026-74947
- CVE-2026-74950
- CVE-2026-74951
- CVE-2026-74952
- CVE-2026-74954
- CVE-2026-74955
- CVE-2026-74956
- CVE-2026-74958
- CVE-2026-74961
- CVE-2026-74966
- CVE-2026-74968
- CVE-2026-74970
- CVE-2026-74975
- CVE-2026-74977
- CVE-2026-74978
- CVE-2026-74979
- CVE-2026-74980
- CVE-2026-74981
- CVE-2026-74982
- CVE-2026-74984
- CVE-2026-74985
- CVE-2026-74986
- CVE-2026-74988
- CVE-2026-74989
- CVE-2026-84637
Frequently Asked Questions
Which Firefox releases need to be updated?
The affected releases are Firefox 153, Firefox ESR 140.13, and Firefox ESR 153.0. The fixes are included in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.
Is exploitation known to be practical?
Mozilla states that some of the internally found bugs showed evidence of memory corruption or another security-relevant defect. It presumes that some could have been exploited with sufficient effort, but the provided information does not describe a specific exploit method or attacker prerequisites.