CVE-2026-8959CRITICAL 9.6EPSS p33.2%

CVE-2026-8959CVE-2026-8959

Description

Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Scoring

CVSS 3.19.6 (CRITICAL)
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
EPSS0.42% probability of exploitation · percentile 33.2% · 2026-06-19T12:03:05Z
Published2026-05-19
Last modified2026-05-20

Underlying weaknesses· 3

CWE-20CWE-119CWE-693

References

  1. https://bugzilla.mozilla.org/show_bug.cgi?id=2034754
  2. https://www.mozilla.org/security/advisories/mfsa2026-46/
  3. https://www.mozilla.org/security/advisories/mfsa2026-48/
  4. https://www.mozilla.org/security/advisories/mfsa2026-50/
  5. https://www.mozilla.org/security/advisories/mfsa2026-51/

3

TypeTargetConfidenceTier
WeaknessImproper Restriction of Operations within the Bounds of a Memory Buffercwe-1190%live
WeaknessImproper Input Validationcwe-200%live
WeaknessProtection Mechanism Failurecwe-6930%live

Related by meaning· 6

Nearest entities by semantic similarity across the cs-graph corpus.

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CVE-2026-8958
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Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.