Vulnerability identifier: #VU58613

Vulnerability risk: Medium

CVSSv3.1: 4.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-43543

CWE-ID: CWE-254

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 an error when handling CSP policies. Documents loaded with the CSP sandbox directive can escape the sandbox's script restriction by embedding additional content.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 90.0 - 94.0.2

Firefox ESR: 91.0 - 91.3.0

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External links
http://www.mozilla.org/en-US/security/advisories/mfsa2021-52/
http://www.mozilla.org/en-US/security/advisories/mfsa2021-53/

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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.