Vulnerability · Published Jun 16, 2026 · Assigned by mozilla
CVE-2026-12304Same-origin policy bypass in the Networking: Cookies component
Critical 9.1
In plain English
A critical-severity security flaw 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 0.2% (higher than 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.2%top 91.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Same-origin policy bypass in the Networking: Cookies component. 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-2026-12304 |
| Debian:13 | firefox-esr | 140.12.0esr-1~deb13u1 | DEBIAN-CVE-2026-12304 |
| Debian:14 | firefox-esr | 140.12.0esr-1 | DEBIAN-CVE-2026-12304 |
| Debian:12 | thunderbird | 1:140.12.0esr-1~deb12u1 | DEBIAN-CVE-2026-12304 |
| Debian:13 | thunderbird | 1:140.12.0esr-1~deb13u1 | DEBIAN-CVE-2026-12304 |
| Debian:14 | thunderbird | 1:140.12.0esr-1 | DEBIAN-CVE-2026-12304 |
| 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-2026-12304 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-12304 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-12304 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-12304 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-12304 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-12304 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | see references |
| Mozilla | Thunderbird | see references |
Weakness: CWE-346 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N