CVE-2026-16389

CRITICAL 9.8CVE-2026-16389 · Published 21/07/2026 · updated 24/10/2026

In short

CVE-2026-16389 is a CRITICAL (CVSS 9.8) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.64%, higher than 50.7% of all vulnerabilities.
Fix: update to 153.0.0, 153.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 153.0.0`	`153.0.0`
thunderbird mozilla	`< 153.0`	`153.0`

Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

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Package

Affected versions

Patched versions

< 153.0.0

153.0.0

< 153.0

153.0

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