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Multiple Vulnerabilities in Mozilla Products Could Allow for Remote Code Execution

MS-ISAC ADVISORY NUMBER:

2018-119

DATE(S) ISSUED:

10/23/2018

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.

November 1 – UPDATED OVERVIEW:
Multiple vulnerabilities have been discovered in Mozilla Thunderbird, the most severe of which could allow for arbitrary code execution. Mozilla Thunderbird is an email client. Successful exploitation of the most severe of these vulnerabilities could allow for arbitrary code execution.

THREAT INTELLIGENCE:

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

SYSTEMS AFFECTED:

  • Mozilla Firefox versions prior to 63
  • Mozilla Firefox ESR versions prior to 60.3
  • November 1 – UPDATED SYSTEMS AFFECTED: Mozilla Thunderbird versions prior to 60.3

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

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 these vulnerabilities are as follows:

  • A potential vulnerability was found in 32-bit builds where an integer overflow during the conversion of scripts to an internal UTF-16 representation could result in allocating a buffer too small for the conversion. This leads to a possible out-of-bounds write. Note: 64-bit builds are not vulnerable to this issue. (CVE-2018-12393)
  • A vulnerability where a WebExtension can run content scripts in disallowed contexts following navigation or other events. This allows for potential privilege escalation by the WebExtension on sites where content scripts should not be run. (CVE-2018-12396)
  • A WebExtension can request access to local files without the warning prompt stating that the extension will "Access your data for all websites" being displayed to the user. This allows extensions to run content scripts in local pages without permission warnings when a local file is opened. (CVE-2018-12397)
  • By rewriting the Host request headers using the webRequest API, a WebExtension can bypass domain restrictions through domain fronting. This would allow access to domains that share a host that are otherwise restricted. (CVE-2018-12395)
  • By using the reflected URL in some special resource URIs, such as chrome:, it is possible to inject stylesheets and bypass Content Security Policy (CSP). (CVE-2018-12398)
  • During HTTP Live Stream playback on Firefox for Android, audio data can be accessed across origins in violation of security policies. Because the problem is in the underlying Android service, this issue is addressed by treating all HLS streams as cross-origin and opaque to access. Note: this issue only affects Firefox for Android. Desktop versions of Firefox are unaffected. (CVE-2018-12391)
  • Memory safety bugs were present that showed evidence of memory corruption. It is presumed that with enough effort that some of these could be exploited to run arbitrary code. (CVE-2018-12390, CVE-2018-12388, CVE-2018-12389)
  • If a site is loaded over a HTTPS connection but loads a favicon resource over HTTP, the mixed content warning is not displayed to users. (CVE-2018-12403)
  • In private browsing mode on Firefox for Android, favicons are cached in the cache/icons folder as they are in non-private mode. This allows information leakage of sites visited during private browsing sessions. Note: this issue only affects Firefox for Android. Desktop versions of Firefox are unaffected. (CVE-2018-12400)
  • SameSite cookies are sent on cross-origin requests when the "Save Page As..." menu item is selected to save a page, violating cookie policy. This can result in saving the wrong version of resources based on those cookies. (CVE-2018-12402)
  • Some special resource URIs will cause a non-exploitable crash if loaded with optional parameters following a '?' in the parsed string. This could lead to denial of service (DOS) attacks. (CVE-2018-12401)
  • When a new protocol handler is registered, the API accepts a title argument which can be used to mislead users about which domain is registering the new protocol. This may result in the user approving a protocol handler that they otherwise would not have. (CVE-2018-12399)
  • When manipulating user events in nested loops while opening a document through script, it is possible to trigger a potentially exploitable crash due to poor event handling. (CVE-2018-12392)

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.

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:

November 1 – UPDATED REFERENCES: Mozilla::
https://www.mozilla.org/en-US/security/advisories/mfsa2018-28/

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