Vulnerability · Published Jun 16, 2026 · Assigned by mozilla
CVE-2026-12327Memory safety bugs fixed in Firefox ESR 140.12, Thunderbird ESR 140.12, Firefox 152 and Thunderbird 152
High 8.1
In plain English
A high-severity memory corruption in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Memory safety bugs present in Firefox ESR 140.11, Thunderbird ESR 140.11, Firefox 151 and Thunderbird 151. 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 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | firefox | 140.12.0-1.el10_2 | ALSA-2026:27733 |
| AlmaLinux:8 | firefox | 140.12.0-1.el8_10.alma.1 | ALSA-2026:27717 |
| AlmaLinux:9 | firefox | 140.12.0-1.el9_8.alma.1 | ALSA-2026:27734 |
| AlmaLinux:9 | firefox-x11 | 140.12.0-1.el9_8.alma.1 | ALSA-2026:27734 |
| AlmaLinux:10 | thunderbird | 140.12.0-1.el10_2.alma.1 | ALSA-2026:30846 |
| AlmaLinux:8 | thunderbird | 140.12.0-1.el8_10.alma.1 | ALSA-2026:33445 |
| AlmaLinux:9 | thunderbird | 140.12.0-1.el9_8.alma.1 | ALSA-2026:29940 |
| Debian:12 | firefox-esr | 140.12.0esr-1~deb12u1 | DEBIAN-CVE-2026-12327 |
| Debian:13 | firefox-esr | 140.12.0esr-1~deb13u1 | DEBIAN-CVE-2026-12327 |
| Debian:14 | firefox-esr | 140.12.0esr-1 | DEBIAN-CVE-2026-12327 |
| Debian:12 | thunderbird | 1:140.12.0esr-1~deb12u1 | DEBIAN-CVE-2026-12327 |
| Debian:13 | thunderbird | 1:140.12.0esr-1~deb13u1 | DEBIAN-CVE-2026-12327 |
| Debian:14 | thunderbird | 1:140.12.0esr-1 | DEBIAN-CVE-2026-12327 |
| Rocky Linux:10 | firefox | 0:140.12.0-1.el10_2 | RLSA-2026:27733 |
| Rocky Linux:8 | firefox | 0:140.12.0-1.el8_10 | RLSA-2026:27717 |
| Rocky Linux:9 | firefox | 0:140.12.0-1.el9_8 | RLSA-2026:27734 |
| Rocky Linux:10 | thunderbird | 0:140.12.0-1.el10_2 | RLSA-2026:30846 |
| Rocky Linux:8 | thunderbird | 0:140.12.0-1.el8_10 | RLSA-2026:33445 |
| Rocky Linux:9 | thunderbird | 0:140.12.0-1.el9_8 | RLSA-2026:29940 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-12327 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-12327 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-12327 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-12327 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-12327 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-12327 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | see references |
| Mozilla | Thunderbird | see references |
Weakness: CWE-119 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- Moderate Severity memory safety bugs fixed in Firefox ESR 140.12, Thunderbird ESR 140.12, Firefox 152 and Thunderbird 152
- https://www.mozilla.org/security/advisories/mfsa2026-57/
- https://www.mozilla.org/security/advisories/mfsa2026-58/
- https://www.mozilla.org/security/advisories/mfsa2026-60/
- https://www.mozilla.org/security/advisories/mfsa2026-61/