There was a way to change the value of JavaScript Object properties that were supposed to be non-writeable. This vulnerability affects Firefox < 144, Firefox ESR < 115.29, Firefox ESR < 140.4, Thunderbird < 144, and Thunderbird < 140.4.
Weakness
The product stores sensitive data in memory that is not locked, or that has been incorrectly locked, which might cause the memory to be written to swap files on disk by the virtual memory manager. This can make the data more accessible to external actors.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Firefox | Mozilla | * | 115.29.0 (excluding) |
| Firefox | Mozilla | * | 144.0 (excluding) |
| Firefox | Mozilla | 116.0 (including) | 140.4.0 (excluding) |
| Thunderbird | Mozilla | * | 140.4.0 (excluding) |
| Thunderbird | Mozilla | 141.0 (including) | 144.0 (excluding) |
| Red Hat Enterprise Linux 10 | RedHat | firefox-0:140.4.0-3.el10_0 | * |
| Red Hat Enterprise Linux 10 | RedHat | thunderbird-0:140.4.0-2.el10_0 | * |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | RedHat | firefox-0:140.4.0-4.el7_9 | * |
| Red Hat Enterprise Linux 8 | RedHat | firefox-0:140.4.0-3.el8_10 | * |
| Red Hat Enterprise Linux 8 | RedHat | thunderbird-0:140.4.0-2.el8_10 | * |
| Red Hat Enterprise Linux 8.2 Advanced Update Support | RedHat | thunderbird-0:140.4.0-2.el8_2 | * |
| Red Hat Enterprise Linux 8.2 Advanced Update Support | RedHat | firefox-0:140.4.0-3.el8_2 | * |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | RedHat | thunderbird-0:140.4.0-2.el8_4 | * |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | RedHat | firefox-0:140.4.0-3.el8_4 | * |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | RedHat | thunderbird-0:140.4.0-2.el8_4 | * |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | RedHat | firefox-0:140.4.0-3.el8_4 | * |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | RedHat | thunderbird-0:140.4.0-2.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | RedHat | firefox-0:140.4.0-3.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Telecommunications Update Service | RedHat | thunderbird-0:140.4.0-2.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Telecommunications Update Service | RedHat | firefox-0:140.4.0-3.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions | RedHat | thunderbird-0:140.4.0-2.el8_6 | * |
| Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions | RedHat | firefox-0:140.4.0-3.el8_6 | * |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | RedHat | thunderbird-0:140.4.0-2.el8_8 | * |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | RedHat | firefox-0:140.4.0-3.el8_8 | * |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | RedHat | thunderbird-0:140.4.0-2.el8_8 | * |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | RedHat | firefox-0:140.4.0-3.el8_8 | * |
| Red Hat Enterprise Linux 9 | RedHat | firefox-0:140.4.0-3.el9_6 | * |
| Red Hat Enterprise Linux 9 | RedHat | thunderbird-0:140.4.0-2.el9_6 | * |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | RedHat | thunderbird-0:140.4.0-2.el9_0 | * |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | RedHat | firefox-0:140.4.0-3.el9_0 | * |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | RedHat | thunderbird-0:140.4.0-2.el9_2 | * |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | RedHat | firefox-0:140.4.0-3.el9_2 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | thunderbird-0:140.4.0-2.el9_4 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | firefox-0:140.4.0-3.el9_4 | * |
| Mozjs102 | Ubuntu | esm-apps/noble | * |
| Mozjs102 | Ubuntu | jammy | * |
| Mozjs102 | Ubuntu | noble | * |
| Mozjs115 | Ubuntu | noble | * |
| Mozjs115 | Ubuntu | plucky | * |
| Mozjs52 | Ubuntu | esm-apps/focal | * |
| Mozjs52 | Ubuntu | esm-infra/bionic | * |
| Mozjs68 | Ubuntu | esm-infra/focal | * |
| Mozjs78 | Ubuntu | esm-apps/jammy | * |
| Mozjs78 | Ubuntu | jammy | * |
| Mozjs91 | Ubuntu | jammy | * |
| Thunderbird | Ubuntu | jammy | * |
Potential Mitigations
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1989978
- https://www.mozilla.org/security/advisories/mfsa2025-81/
- https://www.mozilla.org/security/advisories/mfsa2025-82/
- https://www.mozilla.org/security/advisories/mfsa2025-83/
- https://www.mozilla.org/security/advisories/mfsa2025-84/
- https://www.mozilla.org/security/advisories/mfsa2025-85/
- https://lists.debian.org/debian-lts-announce/2025/10/msg00015.html
- https://lists.debian.org/debian-lts-announce/2025/10/msg00031.html