CVE-2026-5731 Details
Description
Memory safety bugs present in Firefox ESR 115.34.0, 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 and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
A vulnerability has been identified in Mozilla Firefox and Thunderbird, specifically in versions prior to the latest updates. This vulnerability arises from memory safety issues that could lead to memory corruption. With sufficient effort, these issues might be exploited to execute arbitrary code. The vulnerability is present in multiple release channels, including Firefox ESR and Thunderbird ESR.
Users can update to Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, or Thunderbird 140.9.1 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Apr 8, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-119 | Improper Restriction of Operations within the Bounds of a Memory Buffer | CISA-ADP |
| CWE-787 | Out-of-bounds Write | redhat-SADP |
Affected Products
| Product | Versions |
|---|---|
| mozilla firefox | 115.34.0 140.9.0 149.0.1 |
CPE
Remediation
| |
| mozilla thunderbird | 140.9.0 149.0.1 |
CPE
Remediation
| |
Change History
9 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 15, 2026 | CVE Modified | redhat-SADP |
| Jun 30, 2026 | CVE Modified | redhat-SADP |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Apr 16, 2026 | Initial Analysis | [email protected] |
| Apr 13, 2026 | CVE Modified | [email protected] |
| Apr 7, 2026 | CVE Modified | [email protected] |
| Apr 7, 2026 | CVE Modified | CISA-ADP |
| Apr 7, 2026 | New CVE Received | [email protected] |