by Kastro
Paper/Archive/CVE-2026-4701

CVE-2026-4701

Mozilla Firefox — Use-after-free in the JavaScript Engine component

EPSS 0.5%CVSS 9.8
critical.is priorityof 100
38
CVSS 9.8 (ADP, NVD agree)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 41.3.413 × 208.3No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Affected

ProductAffectedFixed inSource
Firefoxsee advisory140.9CNA
Thunderbirdsee advisory140.9CNA

Scores by source

CISA ADP9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refbugzilla.mozilla.org/show_bug.cgi?id=2009303refmozilla.org/security/advisories/mfsa2026-20refmozilla.org/security/advisories/mfsa2026-22refmozilla.org/security/advisories/mfsa2026-23refmozilla.org/security/advisories/mfsa2026-24