Multiple Vulnerabilities in Mozilla Firefox Could Allow for Arbitrary Code Execution

by CIRT Team

DESCRIPTION:
Multiple vulnerabilities have been discovered in Mozilla Firefox,
Firefox Extended Support Release (ESR) and Mozilla Firefox for iOS, 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. Mozilla Firefox for iOS is a web browser used to access
the Internet on Apple Products. Successful exploitation 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.

IMPACT:
Multiple vulnerabilities have been discovered in Mozilla Firefox, and
Firefox Extended Support Release (ESR), and Mozilla Firefox for iOS, the
most severe of which could allow for arbitrary code execution. Details
of these vulnerabilities are as follows:
* File download shares private browsing mode cookies. (CVE-2021-29958)
* When a user has already allowed a website to access microphone and
camera, disabling camera sharing would not fully prevent the website
from re-enabling it without an additional prompt. This was only possible
if the website kept recording with the microphone until re-enabling the
camera. (CVE-2021-29959)
* Firefox used to cache the last filename used for printing a file. When
generating a filename for printing, Firefox usually suggests the web
page title. The caching and suggestion techniques combined may have led
to the title of a website visited during private browsing mode being
stored on disk. (CVE-2021-29960)
* When styling and rendering an oversized <select> element, Firefox did
not apply correct clipping which allowed an attacker to paint over the
user interface. (CVE-2021-29961)
* Firefox for Android would become unstable and hard-to-recover when a
website opened too many popups. NOTE: This bug only affects Firefox for
Android. Other operating systems are unaffected. (CVE-2021-29962)
* Address bar search suggestions in private browsing mode were re-using
session data from normal mode. NOTE: This bug only affects Firefox for
Android. Other operating systems are unaffected. (CVE-2021-29963)
* A locally-installed hostile program could send WM_COPYDATA messages
that Firefox would process incorrectly, leading to an out-of-bounds
read. NOTE: This bug only affects Firefox on Windows. Other operating
systems are unaffected. (CVE-2021-29964)
* A malicious website that causes an HTTP Authentication dialog to be
spawned could trick the built-in password manager to suggest passwords
for the currently active website instead of the website that triggered
the dialog. NOTE: This bug only affects Firefox for Android. Other
operating systems are unaffected. (CVE-2021-29965)
* Mozilla developers Christian Holler, Tooru Fujisawa, Tyson Smith
reported memory safety bugs present in Firefox 88. 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-2021-29966)
* Mozilla developers Christian Holler, Anny Gakhokidze, Alexandru
Michis, Gabriele Svelto reported memory safety bugs present in Firefox
88 and Firefox ESR 78.11. 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-2021-29967)
Successful exploitation 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.

SYSTEM AFFECTED:
* Mozilla Firefox versions prior to 89
* Firefox ESR versions prior to 78.11
* Firefox for iOS versions prior to 34

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:
https://www.mozilla.org/en-US/security/advisories/mfsa2021-23/
https://www.mozilla.org/en-US/security/advisories/mfsa2021-24/
https://www.mozilla.org/en-US/security/advisories/mfsa2021-25/
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29958
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29959
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29960
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29961
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29962
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29963
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29964
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29965
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29966
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29967

CIRT Team