CVE-2019-18906 in Linux Enterprise Server for SAP
Summary
by MITRE • 06/30/2021
A Use of Password Hash Instead of Password for Authentication vulnerability in cryptctl of SUSE Linux Enterprise Server for SAP 12-SP5, SUSE Manager Server 4.0 allows attackers with access to the hashed password to use it without having to crack it. This issue affects: SUSE Linux Enterprise Server for SAP 12-SP5 cryptctl versions prior to 2.4. SUSE Manager Server 4.0 cryptctl versions prior to 2.4.
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Analysis
by VulDB Data Team • 07/04/2021
The vulnerability identified as CVE-2019-18906 represents a critical authentication flaw in the cryptctl utility of SUSE Linux Enterprise Server for SAP and SUSE Manager Server environments. This weakness stems from the improper handling of password authentication mechanisms where the system accepts password hashes directly as valid authentication credentials instead of requiring the actual password input. The flaw exists in cryptctl versions prior to 2.4, creating a scenario where authenticated attackers who gain access to password hash values can bypass normal authentication procedures without needing to perform expensive cryptographic cracking operations.
The technical implementation of this vulnerability falls under CWE-521 Weak Password Requirements, specifically manifesting as improper authentication handling within the cryptographic utilities of enterprise linux distributions. The flaw operates by allowing password hash values to be used in place of actual password inputs during authentication processes, effectively creating a backdoor mechanism that undermines the fundamental security principle of password-based authentication. This vulnerability directly impacts the authentication framework of the affected SUSE products, where the cryptctl utility fails to properly validate whether the provided input represents a genuine password or merely a pre-computed hash value.
From an operational perspective, this vulnerability creates significant risk for organizations running SUSE Enterprise Server for SAP environments, as it allows attackers with access to hash values to authenticate without possessing the actual passwords. The impact extends beyond simple unauthorized access, potentially enabling privilege escalation and lateral movement within affected systems. Attackers who have obtained password hashes through various means such as system breaches, database compromises, or network sniffing can immediately leverage these values to gain authenticated access to systems without the computational overhead of password cracking. This vulnerability particularly affects enterprise environments where password security is paramount and where the compromise of authentication mechanisms can lead to widespread system access.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, specifically targeting the credential access and privilege escalation domains. The attack pattern follows T1110.001 - Brute Force: Password Guessing and T1110.003 - Brute Force: Password Cracking, but with the critical distinction that the attacker bypasses these traditional methods entirely by using the hash values directly. Organizations should implement immediate mitigations including upgrading to cryptctl version 2.4 or later, implementing additional authentication controls such as multi-factor authentication, and conducting comprehensive audits of password hash storage and usage practices. The vulnerability also underscores the importance of proper cryptographic implementation practices and adherence to security standards that prevent such authentication bypass mechanisms from being introduced into enterprise security frameworks.