Full Report
Multiple vulnerabilities have been discovered in Mozilla products, the most severe of which could allow for arbitrary code execution. Mozilla Firefox is a web browser used to access the Internet.Mozilla Firefox ESR is a version of the web browser intended to be deployed in large organizations.Mozilla Thunderbird is an email client.Mozilla Thunderbird ESR is a version of the email client intended to be deployed in large organizations.Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution. Depending on the privileges associated with the user an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.
Analysis Summary
# Vulnerability: Multiple Mozilla Product Vulnerabilities Leading to Arbitrary Code Execution
## CVE Details
- **CVE ID:** CVE-2026-6746, CVE-2026-6747, CVE-2026-6754, CVE-2026-6784, CVE-2026-6785, CVE-2026-6786 (Primary focus on ACE-capable vulnerabilities)
- **CVSS Score:** Not explicitly provided by vendor; Internal Assessment: **High**
- **CWE:** CWE-416 (Use-after-free), CWE-824 (Uninitialized memory), CWE-190 (Integer Overflow), CWE-787 (Out-of-bounds Write)
## Affected Systems
- **Products:**
- Mozilla Firefox
- Mozilla Firefox ESR (Extended Support Release)
- Mozilla Thunderbird
- Mozilla Thunderbird ESR
- **Versions:**
- Firefox versions prior to 150
- Firefox ESR versions prior to 140.10
- Firefox ESR versions prior to 115.35
- Thunderbird versions prior to 150
- Thunderbird ESR versions prior to 140.10
- **Configurations:** Standard installations; impact is significantly higher for accounts operating with administrative privileges.
## Vulnerability Description
Multiple security flaws exist within the Mozilla codebase across various sub-components. The most critical issues involve **Use-after-free (UAF)** bugs in the DOM, WebRTC, and JavaScript Engines, alongside uninitialized memory and boundary condition issues in Graphics and Audio/Video processing.
These flaws allow an attacker to trigger memory corruption. If properly groomed, these conditions can be leveraged to divert execution flow and execute arbitrary machine code within the context of the browser process.
## Exploitation
- **Status:** Not exploited in the wild (as of April 21, 2026).
- **Complexity:** Medium (requires weaponized memory corruption).
- **Attack Vector:** Network (Remote via Drive-by Compromise).
## Impact
- **Confidentiality:** High (Ability to view/exfiltrate local data)
- **Integrity:** High (Ability to modify data or install unauthorized programs)
- **Availability:** High (Ability to crash the application or delete system files)
## Remediation
### Patches
Update to the following versions or later:
- **Firefox:** 150
- **Firefox ESR:** 140.10 or 115.35
- **Thunderbird:** 150
- **Thunderbird ESR:** 140.10
### Workarounds
- **Principle of Least Privilege (PoLP):** Run browser and email clients as a standard user rather than an administrator to limit the scope of a successful compromise.
- **Enhanced Security Settings:** In Thunderbird, disable the "Load Remote Content" feature in emails to prevent automatic triggering of network-based flaws.
## Detection
- **Indicators of Compromise:** Unusual child processes spawned by `firefox.exe` or `thunderbird.exe` (e.g., `cmd.exe` or `powershell.exe`).
- **Detection Methods:** Deploy Endpoint Detection and Response (EDR) tools to monitor for browser-based memory corruption attempts and "Drive-by Compromise" signatures (MITRE T1189).
## References
- **Vendor Advisories:**
- hxxps://www[.]mozilla[.]org/en-US/security/advisories/mfsa2026-30/
- hxxps://www[.]mozilla[.]org/en-US/security/advisories/mfsa2026-31/
- hxxps://www[.]mozilla[.]org/en-US/security/advisories/mfsa2026-32/
- **CVE Database:** hxxps://cve[.]mitre[.]org/cgi-bin/cvename[.]cgi?name=CVE-2026-6746