CVE-2026-4720CRITICAL 9.8EPSS p33.3%

CVE-2026-4720CVE-2026-4720

Description

Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. 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 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Scoring

CVSS 3.19.8 (CRITICAL)
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS0.42% probability of exploitation · percentile 33.3% · 2026-06-19T12:03:05Z
Published2026-03-24
Last modified2026-04-13

Underlying weaknesses· 1

CWE-120

References

  1. https://bugzilla.mozilla.org/buglist.cgi?bug_id=2004652%2C2019372%2C2021922%2C2022567%2C2022733
  2. https://www.mozilla.org/security/advisories/mfsa2026-20/
  3. https://www.mozilla.org/security/advisories/mfsa2026-22/
  4. https://www.mozilla.org/security/advisories/mfsa2026-23/
  5. https://www.mozilla.org/security/advisories/mfsa2026-24/

1

TypeTargetConfidenceTier
WeaknessBuffer Copy without Checking Size of Input ('Classic Buffer Overflow')cwe-1200%live

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Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.