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.

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.

There are currently no reports of these vulnerabilities being exploited in the wild.

Multiple vulnerabilities have been discovered in Mozilla products, the most severe of which could allow for arbitrary code execution. Details of these vulnerabilities are as follows:

Tactic: Initial Access (TA0001):

Technique: Drive-by Compromise (T1189)

• Prevent users from exiting full-screen mode in Firefox Focus for Android. A user who enables full-screen mode on a specially crafted web page could potentially be prevented from exiting full screen mode. This may allow spoofing of other sites as the address bar is no longer visible. This bug only affects Firefox Focus for Android. Other versions of Firefox are unaffected. (CVE-2024-9391)
• A compromised content process could have allowed for the arbitrary loading of cross-origin pages. (CVE-2024-9392)
• Cross-origin access to PDF contents through multipart responses. An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the resource://pdf.js origin. This could allow them to access cross-origin PDF content. This access is limited to “same site” documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. (CVE-2024-9393)
• Cross-origin access to JSON contents through multipart responses. An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the resource://devtools origin. This could allow them to access cross-origin JSON content. This access is limited to “same site” documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. (CVE-2024-9394)
• Memory safety bugs fixed in Firefox 131, Firefox ESR 115.16, Firefox ESR 128.3, Thunderbird 131, and Thunderbird 128.3. 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. (CVE-2024-9401)
• Memory safety bugs fixed in Firefox 131, Firefox ESR 128.3, Thunderbird 131, and Thunderbird 128.3. 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. (CVE-2024-9402)
• Memory safety bugs fixed in Firefox 131 and Thunderbird 131. 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. (CVE-2024-9403)

Additional lower severity vulnerabilities include: 

• Specially crafted filename could be used to obscure download type. A specially crafted filename containing a large number of spaces could obscure the file’s extension when displayed in the download dialog. This bug only affects Firefox for Android. Other versions of Firefox are unaffected. (CVE-2024-9395)
• Potential memory corruption may occur when cloning certain objects. It is currently unknown if this issue is exploitable but a condition may arise where the structured clone of certain objects could lead to memory corruption. (CVE-2024-9396)
• A missing delay in directory upload UI could have made it possible for an attacker to trick a user into granting permission via clickjacking. (CVE-2024-9397)
• External protocol handlers could be enumerated via popups. (CVE-2024-9398)
• Specially crafted WebTransport requests could lead to denial of service. (CVE-2024-9399)
• Potential memory corruption during JIT compilation. (CVE-2024-9400)
• Clipboard write permission bypass. An attacker could write data to the user’s clipboard, bypassing the user prompt, during a certain sequence of navigational events. (CVE-2024-8900)

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.

We recommend the following actions be taken:

• Apply appropriate updates provided by Mozilla to vulnerable systems immediately after appropriate testing. (M1051: Update Software)
• Safeguard 7.1: Establish and Maintain a Vulnerability Management Process: Establish and maintain a documented vulnerability management process for enterprise assets. Review and update documentation annually, or when significant enterprise changes occur that could impact this Safeguard.
• Safeguard 7.4: Perform Automated Application Patch Management: Perform application updates on enterprise assets through automated patch management on a monthly, or more frequent, basis.
• Safeguard 7.7: Remediate Detected Vulnerabilities: Remediate detected vulnerabilities in software through processes and tooling on a monthly, or more frequent, basis, based on the remediation process.
• Safeguard 9.1: Ensure Use of Only Fully Supported Browsers and Email Clients: Ensure only fully supported browsers and email clients are allowed to execute in the enterprise, only using the latest version of browsers and email clients provided through the vendor.

• Apply the Principle of Least Privilege to all systems and services. Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack. (M1026: Privileged Account Management)
• Safeguard 4.7: Manage Default Accounts on Enterprise Assets and Software: Manage default accounts on enterprise assets and software, such as root, administrator, and other pre-configured vendor accounts. Example implementations can include: disabling default accounts or making them unusable.
• Safeguard 5.4: Restrict Administrator Privileges to Dedicated Administrator Accounts: Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet browsing, email, and productivity suite use, from the user’s primary, non-privileged account.

• Use capabilities to detect and block conditions that may lead to or be indicative of a software exploit occurring. (M1050: Exploit Protection)
• Safeguard 10.5: Enable Anti-Exploitation Features: Enable anti-exploitation features on enterprise assets and software, where possible, such as Microsoft® Data Execution Prevention (DEP), Windows® Defender Exploit Guard (WDEG), or Apple® System Integrity Protection (SIP) and Gatekeeper™.

• Restrict use of certain websites, block downloads/attachments, block JavaScript, restrict browser extensions, etc. (M1021: Restrict Web-Based Content)
• Safeguard 9.2: Use DNS Filtering Services: Use DNS filtering services on all enterprise assets to block access to known malicious domains.
• Safeguard 9.3: Maintain and Enforce Network-Based URL Filters: Enforce and update network-based URL filters to limit an enterprise asset from connecting to potentially malicious or unapproved websites. Example implementations include category-based filtering, reputation-based filtering, or through the use of block lists. Enforce filters for all enterprise assets.
• Safeguard 9.6: Block Unnecessary File Types: Block unnecessary file types attempting to enter the enterprise’s email gateway.

• Block execution of code on a system through application control, and/or script blocking. (M1038: Execution Prevention)
• Safeguard 2.5 : Allowlist Authorized Software: Use technical controls, such as application allowlisting, to ensure that only authorized software can execute or be accessed. Reassess bi-annually, or more frequently.
• Safeguard 2.6 : Allowlist Authorized Libraries: Use technical controls to ensure that only authorized software libraries, such as specific .dll, .ocx, .so, etc., files, are allowed to load into a system process. Block unauthorized libraries from loading into a system process. Reassess bi-annually, or more frequently.
• Safeguard 2.7 : Allowlist Authorized Scripts: Use technical controls, such as digital signatures and version control, to ensure that only authorized scripts, such as specific .ps1, .py, etc., files, are allowed to execute. Block unauthorized scripts from executing. Reassess bi-annually, or more frequently.

• Use capabilities to prevent suspicious behavior patterns from occurring on endpoint systems. This could include suspicious process, file, API call, etc. behavior. (M1040: Behavior Prevention on Endpoint)
• Safeguard 13.2 : Deploy a Host-Based Intrusion Detection Solution: Deploy a host-based intrusion detection solution on enterprise assets, where appropriate and/or supported.
• Safeguard 13.7 : Deploy a Host-Based Intrusion Prevention Solution: Deploy a host-based intrusion prevention solution on enterprise assets, where appropriate and/or supported. Example implementations include use of an Endpoint Detection and Response (EDR) client or host-based IPS agent.
• Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources. Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources. (M1017: User Training)
• Safeguard 14.1: Establish and Maintain a Security Awareness Program: Establish and maintain a security awareness program. The purpose of a security awareness program is to educate the enterprise’s workforce on how to interact with enterprise assets and data in a secure manner. Conduct training at hire and, at a minimum, annually. Review and update content annually, or when significant enterprise changes occur that could impact this Safeguard.
• Safeguard 14.2: Train Workforce Members to Recognize Social Engineering Attacks: Train workforce members to recognize social engineering attacks, such as phishing, pre-texting, and tailgating.