Vulnerability identifier: #VU50030

Vulnerability risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-23961

CWE-ID: CWE-200

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 gain access to potentially sensitive information.

The vulnerability exists due to the way Firefox handles requests to internal resources. A remote attacker can create a specially crafted web page and combined with slipstream research techniques collect information about hosts in internal network as well as services running on the user's local machine.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Firefox: 60.0 - 84.0.2

Firefox ESR: 60.0 - 60.9.0, 68.0 - 68.12.0, 78.0 - 78.9.0

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External links
http://www.mozilla.org/en-US/security/advisories/mfsa2021-03/
http://www.mozilla.org/en-US/security/advisories/mfsa2021-15/

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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.