CVE-2016-9639 in Salt
Summary
by MITRE
Salt before 2015.8.11 allows deleted minions to read or write to minions with the same id, related to caching.
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Analysis
by VulDB Data Team • 08/11/2020
The vulnerability identified as CVE-2016-9639 affects SaltStack versions prior to 2015.8.11 and represents a critical security flaw in the distributed configuration management system. This issue stems from improper handling of minion identification and caching mechanisms within the Salt infrastructure, creating a scenario where deleted minions can potentially access and manipulate data from active minions sharing identical identifiers. The vulnerability exploits the caching behavior of Salt's master node, which maintains state information about minions in memory or on disk. When a minion is deleted from the Salt master, its cached information may not be properly invalidated or removed, leaving behind references that can be exploited by malicious actors or compromised systems.
The technical exploitation of this vulnerability occurs through the manipulation of minion IDs, which serve as unique identifiers in Salt's distributed architecture. When multiple minions share the same ID, particularly in scenarios where a previously deleted minion is re-added or when there are ID conflicts, the caching system fails to properly distinguish between legitimate and unauthorized access attempts. This flaw enables what is known as a "cache poisoning" attack where an attacker can leverage the stale cache entries to gain unauthorized access to minion data and execute commands against systems that should be protected from the compromised minion. The vulnerability directly relates to CWE-200, which covers information exposure, and CWE-284, which addresses improper access control, as it allows unauthorized entities to bypass access restrictions through flawed caching mechanisms.
The operational impact of CVE-2016-9639 extends beyond simple data leakage, as it can enable full command execution against affected minions and potentially compromise entire distributed systems. Attackers can exploit this vulnerability to read sensitive configuration data, modify minion states, or execute arbitrary commands on target systems. In large-scale deployments where minion ID management is complex or automated, this vulnerability can be particularly dangerous as it may go unnoticed for extended periods. The attack surface is significantly expanded because the vulnerability exists at the core caching layer of Salt's architecture, affecting all operations that rely on minion identification and authentication. Organizations using SaltStack for critical infrastructure management face potential data breaches, system compromise, and unauthorized access to their distributed computing environments, with impacts ranging from configuration theft to complete system takeover.
Mitigation strategies for CVE-2016-9639 primarily focus on upgrading to SaltStack version 2015.8.11 or later, where the caching and minion ID handling mechanisms have been properly addressed. System administrators should implement strict minion ID management policies, ensuring that minion IDs are unique and properly tracked throughout their lifecycle. Regular cache invalidation procedures should be established, particularly after minion deletion operations, to prevent stale cache entries from being exploited. Network segmentation and access control measures should be implemented to limit the blast radius of potential exploitation, while monitoring systems should be deployed to detect anomalous minion behavior or unauthorized access attempts. Additionally, organizations should conduct regular security audits of their SaltStack configurations and implement proper key management practices to prevent unauthorized minion registration and authentication. The vulnerability demonstrates the critical importance of proper cache invalidation and access control mechanisms in distributed systems, aligning with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting, as it enables attackers to leverage existing legitimate minion identities for unauthorized access.