Remote code execution in Mozilla Firefox and Firefox ESR

Published: 2020-04-03

Risk	Critical
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2020-6819 CVE-2020-6820
CWE-ID	CWE-416
Exploitation vector	Network
Public exploit	Vulnerability #1 is being exploited in the wild. Vulnerability #2 is being exploited in the wild.
Vulnerable software	Mozilla Firefox Client/Desktop applications / Web browsers Firefox ESR Client/Desktop applications / Web browsers
Vendor	Mozilla

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Use-after-free

EUVDB-ID: #VU26573

Risk: Critical

CVSSv3.1: 8.4 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C]

CVE-ID: CVE-2020-6819

CWE-ID: CWE-416 - Use After Free

Exploit availability: No

Description

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a use-after-free error caused by a race condition running the nsDocShell destructor. A remote attacker can create a specially crafted website, trick the victim into visiting it, trigger a use-after-free error and execute arbitrary code on the system.

Successful exploitation of the vulnerability may allow an attacker to compromise vulnerable system.

Note, this vulnerability is being actively exploited in the wild in targeted attacks.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 60.0 - 74.0

Firefox ESR: 60.0 - 68.6.0

CPE2.3

External links

http://www.mozilla.org/en-US/security/advisories/mfsa2020-11/
http://bugzilla.mozilla.org/show_bug.cgi?id=1620818

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to visit a specially crafted website.

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.

2) Use-after-free

EUVDB-ID: #VU26574