CVE-2016-3176 in Salt
Summary
by MITRE
Salt before 2015.5.10 and 2015.8.x before 2015.8.8, when PAM external authentication is enabled, allows attackers to bypass the configured authentication service by passing an alternate service with a command sent to LocalClient.
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Analysis
by VulDB Data Team • 08/08/2020
The vulnerability identified as CVE-2016-3176 represents a critical authentication bypass flaw in the Salt configuration management system that affects versions prior to 2015.5.10 and 2015.8.8. This issue specifically targets environments where PAM external authentication is enabled, creating a significant security risk that can be exploited by malicious actors to circumvent established authentication controls. The flaw resides in how Salt processes authentication requests when communicating with LocalClient, allowing unauthorized access through manipulation of authentication service parameters.
The technical implementation of this vulnerability stems from improper validation of authentication service parameters within Salt's client communication framework. When PAM external authentication is configured, Salt should enforce strict validation of the authentication service being invoked. However, the flaw allows attackers to inject alternate service parameters that override the configured authentication mechanism. This occurs because the system fails to properly sanitize or validate the service name parameter passed during authentication commands, enabling attackers to specify alternative PAM services that may have weaker security controls or different authentication requirements.
The operational impact of this vulnerability is substantial as it directly undermines the integrity of the authentication system within Salt-managed environments. An attacker who can successfully exploit this vulnerability gains unauthorized access to systems managed by Salt without proper authentication, potentially leading to full system compromise. This bypass capability means that even organizations with robust PAM configurations can be rendered vulnerable if they rely on Salt for authentication enforcement. The attack vector is particularly concerning because it requires minimal privileges to execute, as the attacker only needs to be able to send commands to the LocalClient interface.
This vulnerability aligns with CWE-285, which addresses improper authorization in authentication systems, and represents a clear failure in authentication enforcement mechanisms. From an ATT&CK perspective, this flaw maps to privilege escalation and defense evasion techniques, as attackers can bypass authentication controls and potentially maintain persistent access to systems. The vulnerability also demonstrates poor input validation practices that are commonly exploited in authentication bypass scenarios, making it a prime example of how insufficient parameter validation can create security weaknesses in distributed systems.
Organizations should immediately implement mitigations including updating to patched versions of Salt that address this authentication bypass vulnerability. The recommended approach involves upgrading to Salt versions 2015.5.10 or 2015.8.8 and later, which contain the necessary fixes to properly validate authentication service parameters. Additionally, administrators should review and restrict access to LocalClient interfaces to minimize attack surface, implement network segmentation, and ensure that PAM authentication configurations are properly audited. Security monitoring should be enhanced to detect anomalous authentication patterns that might indicate exploitation attempts, particularly focusing on unusual service parameter usage within authentication flows.