CVE-2026-84138

MEDIUM 6.5CVE-2026-84138 · Published 01/09/2026 · updated 03/09/2026

In short

CVE-2026-84138 is a MEDIUM (CVSS 6.5) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.37%, higher than 31.2% of all vulnerabilities.
Fix: update to 155.0.0, 155.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 155.0.0`	`155.0.0`
thunderbird mozilla	`< 155.0`	`155.0`

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

Running one of these products? Scan your site to see whether it exposes a vulnerable version.

Package

Affected versions

Patched versions

< 155.0.0

155.0.0

< 155.0

155.0

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