#VU56373 Input validation error in Mozilla Firefox and Firefox ESR - CVE-2021-38492

Vulnerability identifier: #VU56373

Vulnerability risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-38492

CWE-ID: CWE-20

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 bypass implemented security restrictions.

The vulnerability exists due to insufficient validation of user-supplied input when delegating navigations to the operating system. Firefox accept the mk scheme, which allows a remote attacker to launch pages and execute scripts in Internet Explorer in unprivileged mode.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 60.0 - 91.0.2

Firefox ESR: 60.0 - 60.9.0, 68.0 - 68.12.0, 78.0 - 78.13.0, 91.0 - 91.0.1

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External links
https://www.mozilla.org/en-US/security/advisories/mfsa2021-38/
https://www.mozilla.org/en-US/security/advisories/mfsa2021-39/
https://www.mozilla.org/en-US/security/advisories/mfsa2021-40/

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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.