Authentication bypass in Linux-PAM

1) Improper Authentication

EUVDB-ID: #VU48796

Risk: Medium

CVSSv3.1: 3.4 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-27780

CWE-ID: CWE-287 - Improper Authentication

Exploit availability: No

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 update from vendor's website.

Vulnerable software versions

linux-pam: 1.5.0

External links

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

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.