MS-ISAC CYBERSECURITY ADVISORIES
MS-ISAC ADVISORY NUMBER:
A Vulnerability in Mozilla Firefox Could Allow for Remote Code Execution
A vulnerability has been identified in Mozilla Firefox, Firefox Extended Support Release (ESR), and Thunderbird, which could allow for remote 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 may allow an attacker to execute remote code in the context of the user running the affected application or result in denial-of-service conditions. Depending on the privileges associated with the user, an attacker could install programs; view, change, or delete data; or create new accounts with full user rights.
An exploit built on this vulnerability has been discovered in the wild targeting Tor browser users on Windows. The Tor browser operates through Firefox.
- Mozilla Firefox versions prior to 50.0.2
- Mozilla Firefox ESR prior to 45.5.1
- Thunderbird prior to 45.5.1
- Large and medium government entities:High
- Small government entities:Medium
- Large and medium business entities:High
- Small business entities:Medium
Home users: Low
Successful exploitation may allow an attacker to execute remote code in the context of the user running the affected application or result in denial-of-service conditions. Depending on the privileges associated with the user, an attacker could install programs; view, change, or delete data; or create new accounts with full user rights.
We recommend the following actions be taken:
- Apply appropriate updates provided by Mozilla to vulnerable systems, immediately after appropriate testing.
- Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
- Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
- Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
- Apply the Principle of Least Privilege to all systems and services.