CVE-2026-5734
Memory Corruption in Firefox and Thunderbird Enables Code Execution
Publication date: 2026-04-07
Last updated on: 2026-04-13
Assigner: Mozilla Corporation
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mozilla | firefox | to 149.0.2 (exc) |
| mozilla | firefox | to 140.9.1 (exc) |
| mozilla | thunderbird | to 149.0.2 (exc) |
| mozilla | thunderbird | to 140.9.1 (exc) |
Helpful Resources
Exploitability
| 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. |
| CWE-787 | The product writes data past the end, or before the beginning, of the intended buffer. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability involves memory safety bugs found in specific versions of Firefox and Thunderbird, including Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1, and Thunderbird 149.0.1.
Some of these bugs showed evidence of memory corruption, which means that the software could access or modify memory in unintended ways.
It is presumed that with enough effort, some of these bugs could be exploited by attackers to run arbitrary code on affected systems.
The vulnerability affects Firefox versions earlier than 149.0.2 and Firefox ESR versions earlier than 140.9.1.
How can this vulnerability impact me? :
Exploitation of these memory safety bugs could allow an attacker to execute arbitrary code on your system.
This means that an attacker might be able to take control of your browser or email client, potentially leading to unauthorized access, data theft, or further system compromise.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, update Firefox and Thunderbird to versions that are not affected. Specifically, upgrade Firefox to version 149.0.2 or later, and Firefox ESR to version 140.9.1 or later.