CVE-2026-0878 — Improper Input Validation in Mozilla Firefox

CWE-20 — Improper Input ValidationCWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer12 documents9 sources
Severity
8.0HIGHNVD
EPSS
0.0%
top 92.26%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla ThunderbirdMozilla Firefox
Timeline
PublishedJan 13
Latest updateFeb 2

Description

Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:NExploitability: 1.6 | Impact: 5.8

Affected Packages3 packages

▶NVDmozilla/firefox< 140.7.0+1
▶NVDmozilla/thunderbird< 140.7.0+1
▶Debianmozilla/thunderbird< 1:140.7.0esr-1~deb11u1+3

🔴Vulnerability Details

3
OSV
CVE-2026-0878: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component↗2026-01-13
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CVEList
Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component↗2026-01-13
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GHSA
GHSA-qc2q-rhvg-9278: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component↗2026-01-13
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📋Vendor Advisories

7
Ubuntu
Thunderbird vulnerabilities↗2026-02-02
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Red Hat
firefox: thunderbird: Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL component↗2026-01-13
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Debian
CVE-2026-0878: firefox - Sandbox escape due to incorrect boundary conditions in the Graphics: CanvasWebGL...↗2026
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Mozilla
Mozilla Foundation Security Advisory 2026-04: CVE-2026-0878↗
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Mozilla
Mozilla Foundation Security Advisory 2026-01: CVE-2026-0878↗
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🕵️Threat Intelligence

1
Wiz
CVE-2026-0878 Impact, Exploitability, and Mitigation Steps | Wiz↗
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CVE-2026-0878 — Improper Input Validation in Mozilla | cvebase