CVE-2025-6436 Affecting firefox-esr package, versions <140-r0


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
3.12% (87th percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-FIREFOXESR-17765076
  • published1 Jul 2026
  • disclosed24 Jun 2025

Introduced: 24 Jun 2025

CVE-2025-6436  (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.

Memory safety bugs present in Firefox 139 and Thunderbird 139. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

CVSS Base Scores

version 3.1