CIS Logo
tagline: Confidence in the Connected World

Multiple Vulnerabilities in Mozilla Firefox Could Allow for Arbitrary Code Execution

MS-ISAC ADVISORY NUMBER:

2018-097

DATE(S) ISSUED:

09/05/2018

OVERVIEW:

Multiple vulnerabilities have been discovered in Mozilla Firefox and Firefox Extended Support Release (ESR), 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. 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.

THREAT INTELLIGENCE:

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

SYSTEMS AFFECTED:

  • Mozilla Firefox versions prior to 62
  • Mozilla Firefox ESR versions prior to 60.2

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: MEDIUM
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: MEDIUM
Home Users:
LOW

TECHNICAL SUMMARY:

Multiple vulnerabilities have been discovered in Mozilla Firefox and Firefox Extended Support Release (ESR), the most severe of which could allow for arbitrary code execution. Details of the vulnerabilities are as follows:

  • A use-after-free vulnerability can occur when an IndexedDB index is deleted while still in use by JavaScript code that is providing payload values to be stored. This results in a potentially exploitable crash. (CVE-2018-12378)
  • A use-after-free vulnerability can occur when refresh driver timers are refreshed in some circumstances during shutdown when the timer is deleted while still in use. This results in a potentially exploitable crash. (CVE-2018-12377)
  • Browser proxy settings can be bypassed by using the automount feature with autofs to create a mount point on the local file system. Content can be loaded from this mounted file system directly using a file: URI, bypassing configured proxy settings. Note: this issue only affects OS X in default configurations. On Linux systems, autofs must be installed for the vulnerability to occur and Windows is not affected. (CVE-2017-16541)
  • Memory safety bugs present in Firefox 61 and Firefox ESR 60.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. (CVE-2018-12376)
  • Memory safety bugs present in Firefox 61. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. (CVE-2018-12375)
  • If a user saved passwords before Firefox 58 and then later set a master password, an unencrypted copy of these passwords is still accessible. This is because the older stored password file was not deleted when the data was copied to a new format starting in Firefox 58. The new master password is added only on the new file. This could allow the exposure of stored password data outside of user expectations. (CVE-2018-12383)
  • Manually dragging and dropping an Outlook email message into the browser will trigger a page navigation when the message's mail columns are incorrectly interpreted as a URL. Note: this issue only affects Windows operating systems with Outlook installed. Other operating systems are not affected. (CVE-2018-12381)
  • The displayed addressbar URL can be spoofed on Firefox for Android using a javascript: URI in concert with JavaScript to insert text before the loaded domain name, scrolling the loaded domain out of view to the right. This can lead to user confusion. This vulnerability only affects Firefox for Android. (CVE-2018-12382)
  • When the Mozilla Updater opens a MAR format file which contains a very long item filename, an out-of-bounds write can be triggered, leading to a potentially exploitable crash. This requires running the Mozilla Updater manually on the local system with the malicious MAR file in order to occur. (CVE-2018-12379)

Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution. Depending on the privileges associated with the user group, 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.

RECOMENDATIONS:

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.

REFERENCES:

Get Email Updates When Cyber Threats Like This Arise

Arrow Subscribe to Advisories

Protect Your Systems from Cyber Threats Like This

CIS Control That Helps Avoid This Issue Arrow CIS Control 3: Continuous Vulnerability Assessment and Remediation CIS Benchmark and Other Tools for Related Technology Arrow Mozilla Firefox