#VU49023 Data handling in Mozilla Firefox and Firefox ESR - CVE-2020-35112

Vulnerability identifier: #VU49023

Vulnerability risk: Medium

CVSSv4.0: 4.8 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-35112

CWE-ID: CWE-19

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 the affected system.

The vulnerability exists due to the way Firefox processes downloaded files without extensions on Windows operating system. If a user downloaded a file lacking an extension on Windows, and then "Open"-ed it from the downloads panel, if there was an executable file in the downloads directory with the same name but with an executable extension (such as .bat or .exe) that executable would have been launched instead.

The vulnerability affects Windows installations only.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 60.0 - 83.0

Firefox ESR: 60.0 - 60.9.0, 68.0 - 68.12.0, 78.0 - 78.5.0

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2020-54/
https://www.mozilla.org/en-US/security/advisories/mfsa2020-55/

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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?

No. We are not aware of malware exploiting this vulnerability.