#VU48796 Improper Authentication in linux-pam - CVE-2020-27780

Vulnerability identifier: #VU48796

Vulnerability risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2020-27780

CWE-ID: CWE-287

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
linux-pam
Other software / Other software solutions

Vendor: git.kernel.org

Description

The vulnerability allows a remote attacker to bypass authentication process.

The vulnerability exists due to an error when processing authentication requests in Linux PAM module. A remote or local attacker can bypass authentication process and gain unauthorized access to the application.

Successful exploitation of the vulnerability requires that the account used for authentication does not exists on the system and the password for root account is empty (but root locked down).

Mitigation
Install updates from vendor's website.

Vulnerable software versions

linux-pam: 1.5.0

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External links
https://bugs.gentoo.org/756361
https://www.openwall.com/lists/oss-security/2020/11/24/3
https://github.com/linux-pam/linux-pam/commit/28b8c7045ac8ea4ea080bce02a2df9e3b9e98f06
https://github.com/linux-pam/linux-pam/issues/284

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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.