Cyber Resilience

CVE-2026-8949

High

Published: 19 May 2026

Published
19 May 2026
Modified
20 May 2026
KEV Added
—
Patch
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CVSS Score v3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0058 43.2th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-8949 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 43.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

Integer overflow in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CWE(s)
CWE-190

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
Why these techniques?

Integer overflow in browser UI component enables client-side code execution via malicious content.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v18.1

CVEs Like This One

CVE-2026-8956Same product: Mozilla Firefox
CVE-2026-6783Same product: Mozilla Firefox
CVE-2026-2774Same product: Mozilla Firefox
CVE-2026-2781Same product: Mozilla Firefox
CVE-2026-2762Same product: Mozilla Firefox
CVE-2026-0880Same product: Mozilla Firefox
CVE-2026-8973Same product: Mozilla Firefox
CVE-2026-0891Same product: Mozilla Firefox
CVE-2026-6786Same product: Mozilla Firefox
CVE-2025-9184Same product: Mozilla Firefox

Affected Assets

mozilla
firefox
≤ 140.11.0 · ≤ 151.0.0
mozilla
thunderbird
≤ 140.11 · ≤ 151.0.0

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.

References