#VU57655 Improper Authentication in Nextcloud Server - CVE-2021-41179

Vulnerability identifier: #VU57655

Vulnerability risk: Medium

CVSSv4.0: 4.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-41179

CWE-ID: CWE-287

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Nextcloud Server
Client/Desktop applications / Messaging software

Vendor: Nextcloud

Description

The vulnerability allows a remote attacker to bypass authentication process.

The vulnerability exists due to the Two-Factor Authentication is not enforced for pages marked as public. A remote authenticated attacker can bypass authentication process and gain unauthorized access to sensitive information.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Nextcloud Server: 20.0.0 - 22.1.1

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External links
https://github.com/nextcloud/server/pull/28725
https://hackerone.com/reports/1322865
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7hvh-rc6f-px23

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

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