MULTIPLE VULNERABILITIES IN MOZILLA FIREFOX FOUND

A cybersecurity advisory was issued Wednesday, Oct. 21, 2020, regarding multiple vulnerabilities in Mozilla Firefox. The vulnerabilities could allow an attacker to execute arbitrary code, which could potentially lead to a breach.

What It Is:

Multiple vulnerabilities have been discovered in Mozilla Firefox and Mozilla Firefox 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 in the context of the logged-on user. 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.

Read the original Mozilla Foundation Security Advisory.

Threat Intelligence:

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

Systems Affected:

• Mozilla Firefox versions prior to 81
• Mozilla Firefox ESR versions prior to 78.3

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

What It Means:

If you and/or your business utilize the Mozilla Firefox versions mentioned above, you will need to apply the appropriate updates provided by Mozilla to vulnerable systems immediately following proper testing.

Technical Summary:

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

• A use-after-free bug in the usersctp library was reported upstream. We assume this could have led to memory corruption and a potentially exploitable crash. (CVE-2020-15969)
• In the crossbeam rust crate, the bounded channel incorrectly assumed that Vec::from_iter had allocated capacity that was the same as the number of iterator elements. Vec::from_iter does not actually guarantee that and may allocate extra memory. The destructor of the bounded channel reconstructs Vec from the raw pointer based on the incorrect assumptions - this is unsound and caused a deallocation with the incorrect capacity when Vec::from_iter had allocated different sizes than the number of iterator elements. The impact on Firefox is undetermined, but in another use case, the behavior was causing corruption of jemalloc structures. (CVE-2020-15254)
• If a valid external protocol handler was referenced in an image tag, the resulting broken image size could be distinguished from a broken image size of a non-existent protocol handler. This allowed an attacker to successfully probe whether an external protocol handler was registered. (CVE-2020-15680)
• When multiple WASM threads had a reference to a module, and were looking up exported functions, one WASM thread could have overwritten another's entry in a shared stub table, resulting in a potentially exploitable crash. (CVE-2020-15681)
• When a link to an external protocol was clicked, a prompt was presented that allowed the user to choose what application to open it in. An attacker could induce that prompt to be associated with an origin they didn't control, resulting in a spoofing attack. This was fixed by changing external protocol prompts to be tab-modal while also ensuring they could not be incorrectly associated with a different origin. (CVE-2020-15682)
• Mozilla developers and community members Simon Giesecke, Christian Holler, Philipp, and Jason Kratzer reported memory safety bugs present in Firefox 81 and Firefox ESR 78.3. 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-2020-15683)
• Mozilla developers Christian Holler, Sebastian Hengst, Bogdan Tara, and Tyson Smith reported memory safety bugs present in Firefox 81. 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-2020-15684)

What To Do:

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 untrusted websites or follow links provided by unknown or untrusted sources.
• Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from untrusted sources.
• Apply the Principle of Least Privilege to all systems and services.

Negative Consequences of Lost or Stolen Data:

The loss or theft of proprietary data can have severe impacts, particularly if the compromise becomes public and sensitive information is exposed. Possible impacts include:

• Temporary or permanent loss of sensitive or proprietary information.
• Disruption to regular operations.
• Financial losses incurred to restore systems and files.
• Potential harm to an organization’s reputation.

Should your agency or business need assistance with issues arising from vulnerabilities in Mozilla Firefox including updates and/or patches, Dox can help. Please contact Dox if there is anything we can do to assist in securing your agency, business, or organization.

Thank you for your time and stay safe online.