CVE-2026-84142

Modified Modified - Updated After Analysis

Memory Corruption in Firefox 154

Publication date: 2026-09-01

Last updated on: 2026-09-03

Assigner: Mozilla Corporation

Description

Internally found bugs present in Thunderbird 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 and Thunderbird 155.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-01

Last Modified

2026-09-03

Generated

2026-09-21

AI Q&A

2026-09-01

EPSS Evaluated

2026-09-20

NVD

CVE-2026-84142

EUVD

EUVD-2026-69090

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	to 155.0.0 (exc)
mozilla	thunderbird	to 155.0 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-200	The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
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 154 that showed evidence of memory corruption or other security-relevant defects. With sufficient effort, some of these bugs could potentially be exploited to compromise system security.

Detection Guidance

This vulnerability is specific to Firefox 154 and was fixed in Firefox 155. To detect it, check your Firefox version with commands like 'firefox --version' or 'about:support' in Firefox. If you are running Firefox 154, you are vulnerable.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary code, gain unauthorized access to sensitive data, or perform other malicious actions on affected systems running Firefox 154.

Compliance Impact

This vulnerability does not provide specific details about compliance impacts on standards like GDPR or HIPAA. The description focuses on memory corruption and potential exploitation risks in Firefox 154, but lacks information on regulatory or compliance implications.

Mitigation Strategies

Update Firefox to version 155 or later to address the vulnerability. Remove or disable any affected versions of Firefox from your system.

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