CVE-2025-6424 | Use-after-free in FontFaceSet

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.

Published: 2025-06-24 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-6424 is rated High Risk (67.4/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.10%). High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-6424

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-20 0.25% 1.10% +0.85%
2 2026-03-10 0.16% 0.25% +0.10%
3 2025-12-02 — 0.16% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-6424

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-6424

OS Trackers for CVE-2025-6424

vendor priority summary link
alpine — CVE-2025-6424: 3 source package rows (firefox, firefox-esr, thunderbird); 372 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 372. https://security.alpinelinux.org/vuln/CVE-2025-6424
debian not yet assigned CVE-2025-6424 not yet assigned priority: Debian including 3 source packages (firefox, firefox-esr, thunderbird), 11 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 11. https://security-tracker.debian.org/tracker/CVE-2025-6424
redhat high — https://access.redhat.com/security/cve/CVE-2025-6424
suse high CVE-2025-6424 severity important: SUSE including 80 source package names (2.1.3-4.11:qemu-guest-agent-8.2.7-1.1, MozillaFirefox-140.0-112.270.2, …), 361 product×package rows across 47 product lines (Container suse/sl-micro/6.0/kvm-os-container, Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, … (47 product lines)): Fixed 358, First Fixed 3. https://www.suse.com/security/cve/CVE-2025-6424/
ubuntu medium CVE-2025-6424 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 58 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 28, ignored 10, needs-triage 9, not-affected 9, released 2. https://ubuntu.com/security/CVE-2025-6424

Affected software / configurations for CVE-2025-6424

Vendor Product Version Raw CPE
mozilla firefox < 115.25.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla firefox < 140.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
mozilla firefox >= 116.0, < 128.12.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*

References for CVE-2025-6424

cvelogic Threat Intelligence