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Mozilla Firefox CVE-2026-74949

| EUVDEUVD-2026-60755 HIGH
Use After Free (CWE-416)
2026-08-18 mozilla GHSA-cjxq-c7rj-x436
Privilege Escalation Use After Free Memory Corruption Mozilla
8.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vuln.today AI
8.8 HIGH

Network delivery via malicious webpage; UI:R reflects required victim interaction; S:U consistent with sandboxed renderer model; full C/I/A reflects use-after-free enabling code execution with privilege escalation.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (mozilla).

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

3
Analysis Generated
Aug 18, 2026 - 16:36 vuln.today
CVE Published
Aug 18, 2026 - 12:23 cve.org
HIGH 8.8
CVE Published
Aug 18, 2026 - 12:23 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Privilege escalation due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1.

Articles & Coverage 1

News 12 New Mozilla Vulnerabilities - 12 High Severity, No POC Available Aug 18, 2026

AnalysisAI

Use-after-free memory corruption in Firefox's Canvas2D graphics component enables privilege escalation against any unpatched browser version. Remote unauthenticated attackers can achieve full confidentiality, integrity, and availability impact by delivering a malicious web page to a victim using Firefox prior to version 154 (stable) or the affected ESR releases. No public exploit identified at time of analysis, but the memory corruption class and low attack complexity make this a high-priority patch for both consumer and enterprise Firefox deployments.

Technical ContextAI

The vulnerability resides in Firefox's implementation of the HTML5 Canvas 2D API (Graphics: Canvas2D), a default-enabled browser subsystem used for scriptable 2D rendering. CWE-416 (Use After Free) describes a condition where a memory region is freed but a dangling pointer to it is later dereferenced, allowing an attacker who can control heap layout to redirect execution to attacker-supplied data. Browser use-after-free vulnerabilities in rendering engines are a well-established exploitation class, often chained with heap-spray or type confusion primitives. The CPE string cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* confirms all platforms (Windows, macOS, Linux) across both the stable and ESR release tracks are affected. Three separate Mozilla Security Advisories - mfsa2026-74, mfsa2026-76, and mfsa2026-77 - cover the stable, ESR 140.x, and ESR 153.x channels respectively.

RemediationAI

Upgrade to Firefox 154 (stable), Firefox ESR 140.14, or Firefox ESR 153.1 immediately, as confirmed by Mozilla advisories mfsa2026-74, mfsa2026-76, and mfsa2026-77. Enterprise deployments using the ESR channel should validate which ESR train they are on (140.x or 153.x) and apply the corresponding fix. For environments that cannot patch immediately, restricting end-user access to untrusted or external web content via network proxy policy reduces exposure, with the trade-off of limiting legitimate web access. Disabling JavaScript execution entirely would prevent Canvas2D exploitation but would break virtually all modern web applications and is not practical for most deployments. Browser isolation technologies (e.g., remote browser isolation) can contain exploitation impact to a sandboxed environment. No version rollback is recommended as prior releases carry their own cumulative vulnerability surface.

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Same weakness CWE-416 – Use After Free

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Same technique Privilege Escalation

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
Container suse/kiosk/firefox-esr:140.14-75.12 Affected
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed

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CVE-2026-74949 vulnerability details – vuln.today
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