CVE-2026-4721
Received Received - Intake
Memory Corruption in Firefox and Thunderbird Enables Code Execution

Publication date: 2026-03-24

Last updated on: 2026-04-13

Assigner: Mozilla Corporation

Description
Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-03-24
Last Modified
2026-04-13
Generated
2026-06-16
AI Q&A
2026-03-24
EPSS Evaluated
2026-06-15
NVD
CVE-2026-4721
EUVD
EUVD-2026-14857
Affected Vendors & Products
Showing 5 associated CPEs
Vendor Product Version / Range
mozilla firefox to 149.0 (exc)
mozilla firefox to 115.34.0 (exc)
mozilla firefox From 128.0 (inc) to 140.9.0 (exc)
mozilla thunderbird to 149.0 (exc)
mozilla thunderbird to 140.9.0 (exc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-120 The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability involves memory safety bugs found in specific versions of Firefox and Thunderbird, including Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148, and Thunderbird 148.

Some of these bugs showed evidence of memory corruption, which means that the software's memory could be improperly accessed or modified.

It is presumed that with enough effort, some of these bugs could be exploited to run arbitrary code, potentially allowing an attacker to execute malicious actions on the affected system.

Impact Analysis

The impact of this vulnerability could be severe because exploitation might allow an attacker to run arbitrary code on your system.

This could lead to unauthorized access, data theft, system compromise, or other malicious activities depending on the attacker's intent and the environment in which the software is used.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

I don't know

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-4721. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart