CRITICAL

CVE-2025-6424

Use-after-free in FontFaceSet

CVSS v3

9.8

CRITICAL

EPSS Score

4.4 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

none

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

firefoxAlmaLinux:10all versions · fixed in 128.12.0-1.el10_0
firefoxAlmaLinux:9all versions · fixed in 128.12.0-1.el9_6.alma.1and 1 other package
firefoxAlmaLinux:8all versions · fixed in 128.12.0-1.el8_10.alma.1

Vendor advisories

CVE-2025-6424 Red Hat Product Security253 products fixed · 8 known affected
firefox: thunderbird: Use-after-free in FontFaceSet
rhel10/firefox-flatpak.src as a component of Red Hat Enterprise Linux 10 · rhel10/thunderbird-flatpak.src as a component of Red Hat Enterprise Linux 10 · firefox as a component of Red Hat Enterprise Linux 6
RHSA-2025:10246 Red Hat Product Security13 products fixed
Red Hat Security Advisory: thunderbird security update
RHSA-2025:10196 Red Hat Product Security13 products fixed
Red Hat Security Advisory: thunderbird security update
RHSA-2025:10195 Red Hat Product Security13 products fixed
Red Hat Security Advisory: thunderbird security update
RHSA-2025:10188 Red Hat Product Security17 products fixed
Red Hat Security Advisory: firefox security update
RHSA-2025:10186 Red Hat Product Security11 products fixed
Red Hat Security Advisory: firefox security update

16 more advisories

Full record on NVD

Description

A use-after-free in FontFaceSet resulted in a potentially exploitable crash. This vulnerability was fixed in Firefox 140, Firefox ESR 115.25, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2025-06-24
Last Modified: 2026-04-13

Frequently asked questions

What is CVE-2025-6424?

Is CVE-2025-6424 actively exploited?

Active exploitation of CVE-2025-6424 has not been confirmed. Its EPSS score was 4.4% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-6424?

CVE-2025-6424 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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