Vulnerability · Published Aug 18, 2026 · Assigned by mozilla
CVE-2026-75874Sandbox escape in the Remote Settings Client component
Critical 10.0
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 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)10.0Critical
Exploit odds (30 days)0.5%top 60.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Thunderbird 154, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 140.15, and Thunderbird 153.2.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | firefox | 140.15.0-1.el10_2 | ALSA-2026:67129 |
| AlmaLinux:8 | firefox | 140.15.0-1.el8_10.alma.1 | ALSA-2026:68549 |
| AlmaLinux:9 | firefox | 140.15.0-1.el9_8.alma.1 | ALSA-2026:67133 |
| AlmaLinux:9 | firefox-x11 | 140.15.0-1.el9_8.alma.1 | ALSA-2026:67133 |
| AlmaLinux:10 | thunderbird | 140.16.0-1.el10_2.alma.1 | ALSA-2026:73130 |
| AlmaLinux:8 | thunderbird | 140.16.0-1.el8_10.alma.1 | ALSA-2026:73971 |
| AlmaLinux:9 | thunderbird | 140.16.0-1.el9_8.alma.1 | ALSA-2026:70642 |
| Debian:12 | firefox-esr | 140.15.0esr-1~deb12u1 | DEBIAN-CVE-2026-75874 |
| Debian:13 | firefox-esr | 140.15.0esr-1~deb13u1 | DEBIAN-CVE-2026-75874 |
| Debian:14 | firefox-esr | 140.15.0esr-1 | DEBIAN-CVE-2026-75874 |
| Debian:12 | thunderbird | 1:140.15.0esr-1~deb12u1 | DEBIAN-CVE-2026-75874 |
| Debian:13 | thunderbird | 1:140.15.0esr-1~deb13u1 | DEBIAN-CVE-2026-75874 |
| Debian:14 | thunderbird | 1:153.2.0esr-1 | DEBIAN-CVE-2026-75874 |
| Rocky Linux:10 | firefox | 0:140.15.0-1.el10_2 | RLSA-2026:67129 |
| Rocky Linux:8 | firefox | 0:140.15.0-1.el8_10 | RLSA-2026:68549 |
| Rocky Linux:9 | firefox | 0:140.15.0-1.el9_8 | RLSA-2026:67133 |
| Rocky Linux:10 | thunderbird | 0:140.16.0-1.el10_2 | RLSA-2026:73130 |
| Rocky Linux:8 | thunderbird | 0:140.16.0-1.el8_10 | RLSA-2026:73971 |
| Rocky Linux:9 | thunderbird | 0:140.16.0-1.el9_8 | RLSA-2026:70642 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-75874 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-75874 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-75874 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-75874 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-75874 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-75874 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | see references |
| Mozilla | Thunderbird | see references |
Weakness: CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2039972
- https://www.mozilla.org/security/advisories/mfsa2026-74/
- https://www.mozilla.org/security/advisories/mfsa2026-78/
- https://www.mozilla.org/security/advisories/mfsa2026-83/
- https://www.mozilla.org/security/advisories/mfsa2026-84/
- https://www.mozilla.org/security/advisories/mfsa2026-85/
- https://www.mozilla.org/security/advisories/mfsa2026-87/
- https://www.mozilla.org/security/advisories/mfsa2026-88/