Bug 1901094 (CVE-2020-27780)

Summary: CVE-2020-27780 pam: authentication bypass when the user doesn't exist and root password is blank
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: besser82, ipedrosa, pbrezina, tmraz
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: pam 1.5.1 Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in Linux-PAM in the way it handles empty passwords for non-existing users. When the user doesn't exist, PAM tries to authenticate with root and with an empty password, authentication is successful. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2020-11-24 17:34:06 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 1901173    
Bug Blocks: 1900800    

Description Guilherme de Almeida Suckevicz 2020-11-24 13:41:15 UTC 
A flaw was found in Linux-Pam in the way it handle empty passwords for non-existing users. When the user doesn't exist PAM try to authenticate with root and in the case of an empty password it successfully authenticate.

Reference:
https://github.com/linux-pam/linux-pam/issues/284

Upstream patch:
https://github.com/linux-pam/linux-pam/pull/300
Comment 1 Stefan Cornelius 2020-11-24 16:25:18 UTC 
Introduced in version 1.5.0.
Comment 2 Stefan Cornelius 2020-11-24 16:32:01 UTC 
Created pam tracking bugs for this issue:

Affects: fedora-all [bug 1901173]
Comment 3 Product Security DevOps Team 2020-11-24 17:34:06 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2020-27780