CVE-2026-2778 — Improper Restriction of Operations within the Bounds of a Memory Buffer in Mozilla Firefox

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer13 documents9 sources
Severity
10.0CRITICALNVD
EPSS
0.1%
top 76.88%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla ThunderbirdMozilla Firefox
Timeline
PublishedFeb 24

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HExploitability: 3.9 | Impact: 6.0

Affected Packages3 packages

▶NVDmozilla/firefox128.0 — 140.8.0+2
▶NVDmozilla/thunderbird< 140.8.0+1
▶Debianmozilla/thunderbird< 1:140.8.0esr-1~deb11u1+3

🔴Vulnerability Details

3
GHSA
GHSA-3qgm-jcxp-m9m6: Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component↗2026-02-24
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CVEList
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component↗2026-02-24
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OSV
CVE-2026-2778: Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component↗2026-02-24
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📋Vendor Advisories

7
Red Hat
firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component↗2026-02-24
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Debian
CVE-2026-2778: firefox - Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML comp...↗2026
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Mozilla
Mozilla Foundation Security Advisory 2026-16: CVE-2026-2778↗
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Mozilla
Mozilla Foundation Security Advisory 2026-13: CVE-2026-2778↗
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Mozilla
Mozilla Foundation Security Advisory 2026-14: CVE-2026-2778↗
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🕵️Threat Intelligence

1
Wiz
CVE-2026-2778 Impact, Exploitability, and Mitigation Steps | Wiz↗
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💬Community

1
Bugzilla
CVE-2026-2778 firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component↗2026-02-24
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CVE-2026-2778 — Mozilla Firefox vulnerability | cvebase