CVE-2026-5734: Vulnerability in Mozilla Firefox
Memory safety bugs present in 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 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
AI Analysis
Technical Summary
This vulnerability consists of memory safety bugs in specific versions of Firefox ESR and Thunderbird ESR as well as Firefox and Thunderbird releases. Some bugs showed evidence of memory corruption, which could be exploited to execute arbitrary code with sufficient effort. The CVSS 3.1 score is 8.1, indicating high impact with network attack vector, high complexity, no privileges required, no user interaction, and high confidentiality, integrity, and availability impacts. Mozilla released official fixes in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2, and Thunderbird 149.0.2 to address these issues.
Potential Impact
Successful exploitation of these memory safety bugs could lead to arbitrary code execution, compromising confidentiality, integrity, and availability of affected systems. The vulnerability is remotely exploitable without privileges or user interaction but requires high attack complexity. There are no known exploits in the wild at this time.
Mitigation Recommendations
Official fixes are available and have been released by Mozilla in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2, and Thunderbird 149.0.2. Users and administrators should update to these versions or later to remediate the vulnerability. No additional mitigation actions are indicated by the vendor advisory.
CVE-2026-5734: Vulnerability in Mozilla Firefox
Description
Memory safety bugs present in 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 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
CVSS v3.1
Score 8.1high
Affected software
pkg:github/mozilla/firefoxRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability consists of memory safety bugs in specific versions of Firefox ESR and Thunderbird ESR as well as Firefox and Thunderbird releases. Some bugs showed evidence of memory corruption, which could be exploited to execute arbitrary code with sufficient effort. The CVSS 3.1 score is 8.1, indicating high impact with network attack vector, high complexity, no privileges required, no user interaction, and high confidentiality, integrity, and availability impacts. Mozilla released official fixes in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2, and Thunderbird 149.0.2 to address these issues.
Potential Impact
Successful exploitation of these memory safety bugs could lead to arbitrary code execution, compromising confidentiality, integrity, and availability of affected systems. The vulnerability is remotely exploitable without privileges or user interaction but requires high attack complexity. There are no known exploits in the wild at this time.
Mitigation Recommendations
Official fixes are available and have been released by Mozilla in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2, and Thunderbird 149.0.2. Users and administrators should update to these versions or later to remediate the vulnerability. No additional mitigation actions are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-04-07T12:43:14.328Z
- 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/mfsa2026-27/","vendor":"Mozilla"}]
Threat ID: 69d50016aaed68159a219ce2
Added to database: 04/07/2026, 13:01:10 UTC
Last enriched: 07/15/2026, 09:34:43 UTC
Last updated: 07/31/2026, 19:22:59 UTC
Views: 208
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