Firefox vulnerability could allow for arbitrary code execution

Fortify Security Team
Feb 8, 2021

OVERVIEW:
A vulnerability has been discovered in Mozilla Firefox and Firefox ESR, which could allow for arbitrary code execution. Mozilla Firefox is a web browser used to access the internet. Firefox ESR is a version of the web browser intended to be deployed in large organizations. Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code in the context of the browser. Depending on the privileges associated with the application, an attacker could view, change, or delete data. If this application has been configured to have fewer user rights on the system, exploitation of the vulnerability could have less impact than if it was configured with administrative rights.

THREAT INTELLIGENCE:
There are currently reports of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

  • Mozilla Firefox versions prior to 85.0.1
  • Firefox ESR versions prior to 78.7.1

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:
A vulnerability has been discovered in Mozilla Firefox and Firefox ESR, which could allow for arbitrary code execution. This vulnerability exists in the Angle graphics library where the depth pitch computations fail to take into account the block size and simply multiplies the row pitch with the pixel height. This causes the load functions to use a very high depth pitch, reading past the end of the user-supplied buffer.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code in the context of the browser. Depending on the privileges associated with this application, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. If this application has been configured to have fewer user rights on the system, exploitation of this vulnerability could have less impact than if it was configured with administrative rights.

RECOMMENDATIONS:
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:
Mozilla:
https://www.mozilla.org/en-US/security/advisories/mfsa2021-06/

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