CVE-2026-74987

Modified Modified - Updated After Analysis

Memory Corruption in Firefox ESR and Firefox

Publication date: 2026-08-18

Last updated on: 2026-09-01

Assigner: Mozilla Corporation

Description

Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. 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 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-18

Last Modified

2026-09-01

Generated

2026-09-08

AI Q&A

2026-08-18

EPSS Evaluated

2026-09-06

NVD

CVE-2026-74987

EUVD

EUVD-2026-60672

Affected Vendors & Products

Vendor	Product	Version / Range
mozilla	firefox	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	From 141.0 (inc) to 153.1.0 (exc)
mozilla	thunderbird	to 140.14.0 (exc)
mozilla	firefox	to 140.14.0 (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 ESR 140.13, Firefox ESR 153.0, and Firefox 153. Some bugs showed evidence of memory corruption or other security-relevant defects. With enough effort, some could potentially be exploited to compromise system security.

Detection Guidance

This vulnerability affects Firefox ESR versions 140.13, 153.0, and Firefox 153. No specific detection commands are provided in the context. Check installed Firefox versions with commands like 'firefox --version' or 'apt list --installed | grep firefox' to identify vulnerable versions.

Impact Analysis

If exploited, this vulnerability could allow attackers to execute arbitrary code, gain unauthorized access, or cause system crashes. Users running affected Firefox versions may face data breaches, malware infections, or loss of sensitive information.

Compliance Impact

This vulnerability could lead to unauthorized data access or leaks, violating GDPR's data protection requirements or HIPAA's safeguards for protected health information. Organizations may face fines or legal penalties if affected systems handle regulated data.

Mitigation Strategies

Update Firefox to version 154 or later, Firefox ESR 140.14, or Firefox ESR 153.1. Disable automatic updates temporarily if needed, then verify the update with 'firefox --version'.

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