#VU26573 Use-after-free in Mozilla Firefox and Firefox ESR - CVE-2020-6819

Vulnerability identifier: #VU26573

Vulnerability risk: Critical

CVSSv4.0: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:A/U:Red]

CVE-ID: CVE-2020-6819

CWE-ID: CWE-416

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Mozilla Firefox
Client/Desktop applications / Web browsers
Firefox ESR
Client/Desktop applications / Web browsers

Vendor: Mozilla

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 - 60.9.0, 68.0 - 68.6.0

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

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Q & A

Can this vulnerability be exploited remotely?

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

Is there known malware, which exploits this vulnerability?

Yes. This vulnerability is being exploited in the wild.