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Firefox CVE-2026-84120

| EUVDEUVD-2026-69065 MEDIUM
Use After Free (CWE-416)
2026-09-01 mozilla GHSA-8rw8-779w-6fpc
Information Disclosure Use After Free Memory Corruption Red Hat Mozilla Suse
5.4
CVSS 3.1 · Vendor: mozilla
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Severity by source

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

Browser media UAF is network-triggered with no auth (PR:N) but requires user to visit a page (UI:R); impact bounded to partial heap read and limited write, no availability loss.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative
Red Hat
8.8 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
Low
Integrity
Low
Availability
None

Lifecycle Timeline

4
Analysis Generated
Sep 01, 2026 - 15:19 vuln.today
CVSS changed
Sep 01, 2026 - 14:22 NVD
5.4 (None) 5.4 (MEDIUM)
CVE Published
Sep 01, 2026 - 12:18 cve.org
UNKNOWN (no severity yet)
CVE Published
Sep 01, 2026 - 12:18 cve.org
MEDIUM 5.4

DescriptionCVE.org

Use-after-free in the Audio/Video component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2.

AnalysisAI

Use-after-free in Firefox's Audio/Video component exposes users running Firefox prior to version 155 and affected ESR branches to potential heap memory disclosure and limited data modification when processing attacker-controlled media. The vulnerability is network-reachable but requires user interaction - visiting a malicious or compromised page that triggers media playback - and carries a CVSS score of 5.4 reflecting bounded C:L/I:L impact with no availability loss. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires an end user to actively visit a page hosting attacker-controlled audio or video content and trigger media playback - confirmed by the CVSS UI:R metric. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS vector (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N) places this as a moderate network-reachable issue with no authentication barrier but a mandatory user-interaction gate, capping real-world automatable reach. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Standard release users should upgrade to Firefox 155 or later. … Detailed patch versions, workarounds, and compensating controls in full report.
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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected

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CVE-2026-84120 vulnerability details – vuln.today
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