CVE-2026-84145

Analyzed Analyzed - Analysis Complete

Memory Corruption in Firefox

Publication date: 2026-09-01

Last updated on: 2026-09-03

Assigner: Mozilla Corporation

Description

Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird 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 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-01

Last Modified

2026-09-03

Generated

2026-09-22

AI Q&A

2026-09-01

EPSS Evaluated

2026-09-20

NVD

CVE-2026-84145

EUVD

EUVD-2026-69068

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 154.0.0 (inc) to 155.0.0 (exc)
mozilla	thunderbird	From 154.0 (inc) to 155.0 (exc)
mozilla	firefox	From 141.0.0 (inc) to 153.2.0 (exc)
mozilla	thunderbird	to 140.15.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.2.0 (exc)
mozilla	firefox	to 115.40.0 (exc)
mozilla	firefox	From 116.0 (inc) to 140.15.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-119	The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Attack-Flow Graph

Executive Summary

This vulnerability involves internally found bugs in Firefox versions 154, ESR 153.1, ESR 140.14, and ESR 115.39. Some bugs showed evidence of memory corruption or other security defects, which could potentially be exploited with sufficient effort. It was fixed in Firefox 155 and newer ESR versions.

Detection Guidance

This vulnerability affects specific versions of Firefox and Firefox ESR. To detect it, check the installed version of Firefox on your system. If you are running Firefox 154, Firefox ESR 153.1, Firefox ESR 140.14, or Firefox ESR 115.39, your system is vulnerable. Update to Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, or Firefox ESR 153.2 to remediate the issue.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary code, gain unauthorized access, or cause system crashes. Users running vulnerable Firefox versions are at risk of security breaches or malware infections.

Compliance Impact

This vulnerability involves memory corruption and potential security defects in Firefox versions, which could lead to unauthorized access or data breaches. Such issues may impact compliance with GDPR by risking personal data exposure and HIPAA by compromising protected health information if exploited.

Mitigation Strategies

Update Firefox to version 155 or later, Firefox ESR 115.40 or later, Firefox ESR 140.15 or later, or Firefox ESR 153.2 or later to address the memory corruption and security defects.

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