Vulnerability · Published Feb 24, 2026 · Assigned by mozilla
CVE-2026-2778Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component
Critical 10.0
In plain English
A critical-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 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)10.0Critical
Exploit odds (30 days)0.6%top 53.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | firefox | 140.8.0-2.el10_1 | ALSA-2026:3361 |
| AlmaLinux:8 | firefox | 140.8.0-2.el8_10.alma.1 | ALSA-2026:3338 |
| AlmaLinux:9 | firefox | 140.8.0-2.el9_7.alma.1 | ALSA-2026:3339 |
| AlmaLinux:9 | firefox-x11 | 140.8.0-2.el9_7.alma.1 | ALSA-2026:3339 |
| AlmaLinux:10 | thunderbird | 140.8.0-2.el10_1.alma.1 | ALSA-2026:3517 |
| AlmaLinux:8 | thunderbird | 140.8.0-1.el8_10.alma.1 | ALSA-2026:3515 |
| AlmaLinux:9 | thunderbird | 140.8.0-1.el9_7.alma.1 | ALSA-2026:3516 |
| Debian:12 | firefox-esr | 140.8.0esr-1~deb12u1 | DSA-6148-1 |
| Debian:12 | firefox-esr | 140.8.0esr-1~deb12u1 | DEBIAN-CVE-2026-2778 |
| Debian:13 | firefox-esr | 140.8.0esr-1~deb13u1 | DEBIAN-CVE-2026-2778 |
| Debian:13 | firefox-esr | 140.8.0esr-1~deb13u1 | DSA-6148-1 |
| Debian:14 | firefox-esr | 140.8.0esr-1 | DEBIAN-CVE-2026-2778 |
| Debian:12 | thunderbird | 1:140.8.0esr-1~deb12u1 | DSA-6152-1 |
| Debian:12 | thunderbird | 1:140.8.0esr-1~deb12u1 | DEBIAN-CVE-2026-2778 |
| Debian:13 | thunderbird | 1:140.8.0esr-1~deb13u1 | DEBIAN-CVE-2026-2778 |
| Debian:13 | thunderbird | 1:140.8.0esr-1~deb13u1 | DSA-6152-1 |
| Debian:14 | thunderbird | 1:140.8.0esr-1 | DEBIAN-CVE-2026-2778 |
| Rocky Linux:10 | firefox | 0:140.8.0-2.el10_1 | RLSA-2026:3361 |
| Rocky Linux:8 | firefox | 0:140.8.0-2.el8_10 | RLSA-2026:3338 |
| Rocky Linux:9 | firefox | 0:140.8.0-2.el9_7 | RLSA-2026:3339 |
| Rocky Linux:10 | thunderbird | 0:140.8.0-2.el10_1 | RLSA-2026:3517 |
| Rocky Linux:8 | thunderbird | 0:140.8.0-1.el8_10 | RLSA-2026:3515 |
| Rocky Linux:9 | thunderbird | 0:140.8.0-1.el9_7 | RLSA-2026:3516 |
| Ubuntu:22.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-2778 |
| Ubuntu:24.04:LTS | mozjs102 | no fix listed | UBUNTU-CVE-2026-2778 |
| Ubuntu:24.04:LTS | mozjs115 | no fix listed | UBUNTU-CVE-2026-2778 |
| Ubuntu:22.04:LTS | mozjs78 | no fix listed | UBUNTU-CVE-2026-2778 |
| Ubuntu:22.04:LTS | mozjs91 | no fix listed | UBUNTU-CVE-2026-2778 |
| Ubuntu:22.04:LTS | thunderbird | no fix listed | UBUNTU-CVE-2026-2778 |
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:L/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2016358
- https://www.mozilla.org/security/advisories/mfsa2026-13/
- https://www.mozilla.org/security/advisories/mfsa2026-14/
- https://www.mozilla.org/security/advisories/mfsa2026-15/
- https://www.mozilla.org/security/advisories/mfsa2026-16/
- https://www.mozilla.org/security/advisories/mfsa2026-17/
- https://access.redhat.com/security/cve/CVE-2026-2778 vdb-entry, x_refsource_REDHAT
- RHBZ#2442335 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2778.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:3984 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3976 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:4260 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3361 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3517 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3338 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3515 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3492 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:4432 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3491 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3980 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3495 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3979 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3494 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:4022 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3493 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3983 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:4152 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3978 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3496 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3981 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3497 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3982 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3339 vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:3516 vendor-advisory, x_refsource_REDHAT