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Mozilla Firefox CVE-2026-84142

| EUVDEUVD-2026-69090 CRITICAL
Buffer Overflow (CWE-119)
2026-09-01 mozilla GHSA-jc69-hhhc-c4h9
Buffer Overflow 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 reachable via the network but requiring the victim to load malicious content (UI:R) and non-trivial, presumed-only exploitation (AC:H); full impact if code execution is achieved.

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

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 - 16:15 vuln.today
CVSS changed
Sep 03, 2026 - 16:07 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. 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.

AnalysisAI

Memory-corruption defects in Mozilla Firefox 154 were discovered internally by Mozilla and bundled under CVE-2026-84142 (advisories MFSA2026-82 and MFSA2026-86), and fixed in Firefox 155. Several of the reported Bugzilla issues showed evidence of memory corruption that Mozilla presumes could have been exploited with sufficient effort to achieve code execution when a user renders malicious web content. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Delivery
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Exploit
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Execution
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Vulnerability AssessmentAI

Exploitation Exploitation requires a Firefox 154 user to load attacker-controlled web content (a malicious or compromised page/resource) that reaches the vulnerable code path - so despite the CVSS UI:N marking, realistic exploitation depends on user interaction (navigation/rendering). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The input CVSS of 9.8 (AV:N/AC:L/PR:N/UI:N/C:H/I:H/A:H) overstates real-world risk for a browser memory-safety batch: browsers are client applications, so a victim must actively load malicious web content, which in practice implies user interaction (UI:R) and non-trivial exploit engineering (AC:H) - Mozilla itself only says the bugs 'could have been exploited' with effort, not that a working exploit exists. … 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, which contains the fixes per MFSA2026-82 and MFSA2026-86; this is the primary and recommended remediation. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, conduct a complete inventory of Firefox 154 installations across all business units and notify affected users of the critical vulnerability requiring patching. …

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Same weakness CWE-119 – Buffer Overflow

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8.8
CVE-2023-4966 HIGH POC
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CVE-2017-11774 HIGH POC
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Same technique Buffer Overflow

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CVE-2015-5119 CRITICAL POC
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CVE-2015-3113 CRITICAL POC
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CVE-2020-0796 CRITICAL POC
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CVE-2019-11043 CRITICAL POC
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CVE-2009-0927 HIGH POC
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CVE-2012-1889 HIGH POC
8.8

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-2026-84142 vulnerability details – vuln.today
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