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Mozilla Firefox CVE-2026-84143

| EUVDEUVD-2026-69091 CRITICAL
Buffer Overflow (CWE-119)
2026-09-01 mozilla GHSA-hcr8-q9p9-c49f
Buffer Overflow Red Hat Mozilla Suse
9.8
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
7.5 HIGH

Browser memory-corruption requires loading hostile web content (UI:R) and exploitability is unproven/non-trivial (AC:H); successful exploitation yields full impact on the browser process (C/I/A:H).

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

Primary rating from NVD.

CVSS VectorNVD

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

Lifecycle Timeline

4
Analysis Generated
Sep 03, 2026 - 15:58 vuln.today
CVSS changed
Sep 03, 2026 - 15:52 NVD
9.8 (CRITICAL)
CVE Published
Sep 01, 2026 - 12:19 cve.org
UNKNOWN (no severity yet)
CVE Published
Sep 01, 2026 - 12:19 nvd
CRITICAL 9.8

DescriptionNVD

Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, and Firefox ESR 153.2.

AnalysisAI

Memory corruption in Mozilla Firefox 154, Firefox ESR 153.1, and Firefox ESR 140.14 stems from a batch of internally discovered memory-safety defects that Mozilla presumes could be exploited to run arbitrary code within the browser process. The flaws were found by Mozilla's own developers and fuzzing efforts (no external report), affect the mainline and both ESR trains, and are resolved in Firefox 155, ESR 140.15, and ESR 153.2. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires the victim to load attacker-controlled web content in a vulnerable build (Firefox 154, ESR 153.1, or ESR 140.14) - i.e., visiting a malicious/compromised site or rendering hostile embedded content, which constitutes user interaction. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS 9.8 (AV:N/AC:L/PR:N/UI:N) reads as fully remote, no-interaction, no-privilege RCE - but this is almost certainly overstated for a client-side browser memory-corruption bug. … 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 Vendor-released patch: upgrade to Firefox 155 (mainline), Firefox ESR 140.15, or Firefox ESR 153.2 per the corresponding Mozilla Foundation Security Advisories (mfsa2026-82/84/85/86/87/88). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, identify all systems running Firefox 154, Firefox ESR 153.1, or Firefox ESR 140.14 and communicate the vulnerability to stakeholders. …

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Same weakness CWE-119 – Buffer Overflow

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Same technique Buffer Overflow

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected

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CVE-2026-84143 vulnerability details – vuln.today
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