CVE-2025-6434 Affecting firefox-esr package, versions <140-r0


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.23% (14th percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-FIREFOXESR-17764302
  • published1 Jul 2026
  • disclosed24 Jun 2025

Introduced: 24 Jun 2025

CVE-2025-6434  (opens in a new tab)

How to fix?

Upgrade Chainguard firefox-esr to version 140-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream firefox-esr package and not the firefox-esr package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

The exception page for the HTTPS-Only feature, displayed when a website is opened via HTTP, lacked an anti-clickjacking delay, potentially allowing an attacker to trick a user into granting an exception and loading a webpage over HTTP. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVSS Base Scores

version 3.1