CVE-2026-5731: Vulnerability in Mozilla Firefox
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.
AI Analysis
Technical Summary
This vulnerability involves multiple memory safety bugs in Mozilla Firefox and Thunderbird versions prior to the fixed releases. The bugs showed evidence of memory corruption, which could be exploited to run arbitrary code with no user interaction required. Affected versions include Firefox ESR 115.34.0, 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1, and Thunderbird 149.0.1. Mozilla fixed these issues in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. The vulnerability is tracked as CVE-2026-5731 with a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating high impact on confidentiality, integrity, and availability.
Potential Impact
Successful exploitation of these memory safety bugs could allow an attacker to execute arbitrary code remotely without user interaction, potentially leading to full compromise of the affected application. The vulnerabilities impact confidentiality, integrity, and availability of the affected systems. No known exploits are currently reported in the wild.
Mitigation Recommendations
Mozilla has released official fixes for these vulnerabilities in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. Users and administrators should update to these versions or later to remediate the vulnerabilities. Patch status is confirmed by Mozilla advisories. No additional mitigation steps are required beyond applying the official updates.
CVE-2026-5731: Vulnerability in Mozilla Firefox
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves multiple memory safety bugs in Mozilla Firefox and Thunderbird versions prior to the fixed releases. The bugs showed evidence of memory corruption, which could be exploited to run arbitrary code with no user interaction required. Affected versions include Firefox ESR 115.34.0, 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1, and Thunderbird 149.0.1. Mozilla fixed these issues in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. The vulnerability is tracked as CVE-2026-5731 with a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating high impact on confidentiality, integrity, and availability.
Potential Impact
Successful exploitation of these memory safety bugs could allow an attacker to execute arbitrary code remotely without user interaction, potentially leading to full compromise of the affected application. The vulnerabilities impact confidentiality, integrity, and availability of the affected systems. No known exploits are currently reported in the wild.
Mitigation Recommendations
Mozilla has released official fixes for these vulnerabilities in Firefox 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. Users and administrators should update to these versions or later to remediate the vulnerabilities. Patch status is confirmed by Mozilla advisories. No additional mitigation steps are required beyond applying the official updates.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-04-07T12:43:11.413Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-25/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-26/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-27/","vendor":"Mozilla"}]
Threat ID: 69d50016aaed68159a219cd3
Added to database: 4/7/2026, 1:01:10 PM
Last enriched: 4/15/2026, 12:07:51 PM
Last updated: 5/22/2026, 9:53:42 AM
Views: 154
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