Instituto Nacional de ciberseguridad. Sección Incibe
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CVE-2026-4721

Severity CVSS v4.0:
Pending analysis
Type:
CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Publication date:
24/03/2026
Last modified:
25/03/2026

Description

Memory safety bugs present in Firefox ESR 115.33, 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 affects Firefox

Impact

Vector 3.x
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS v3.1 Severity and Metrics:

Base Score: 9.80 CRITICAL
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): High

Base Score 3.x
9.80
Severity 3.x
CRITICAL

Vulnerable products and versions

CPE From Up to
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* 115.34.0 (excluding)
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* 149.0 (excluding)
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* 128.0 (including) 140.9.0 (excluding)
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* 140.9.0 (excluding)
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* 149.0 (excluding)

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools