CVE-2016-3104 in MongoDB
Summary
by MITRE
mongod in MongoDB 2.6, when using 2.4-style users, and 2.4 allow remote attackers to cause a denial of service (memory consumption and process termination) by leveraging in-memory database representation when authenticating against a non-existent database.
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Analysis
by VulDB Data Team • 08/31/2020
The vulnerability described in CVE-2016-3104 represents a critical denial of service flaw affecting MongoDB database servers running version 2.6 with 2.4-style user authentication. This issue specifically manifests when the database system processes authentication requests against non-existent databases, creating a scenario where malicious actors can exploit the system's handling of in-memory database representations. The flaw operates through the authentication mechanism's interaction with database state management, where the system fails to properly handle cases where authentication attempts target databases that do not exist within the current database instance.
The technical implementation of this vulnerability stems from how MongoDB's authentication subsystem manages memory allocation and database representation during user validation processes. When an authentication request is made against a non-existent database, the system's internal state management creates an inconsistent memory representation that leads to excessive memory consumption patterns. This memory leak occurs because the authentication process attempts to maintain internal database objects and metadata structures even when the target database does not exist, causing the system to allocate resources that are never properly released. The vulnerability is particularly dangerous because it leverages the legacy 2.4-style user authentication model, which was maintained for backward compatibility but contained implementation flaws that persist in the 2.6 version.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromising the overall stability and availability of MongoDB instances. Attackers can repeatedly exploit this flaw to consume system resources until the database process terminates due to memory exhaustion, effectively creating a denial of service condition. This attack vector is particularly concerning because it requires minimal privileges and can be executed remotely, making it accessible to any attacker with network access to the MongoDB service. The vulnerability affects systems where 2.4-style user authentication is enabled, which represents a significant portion of MongoDB installations due to the backward compatibility features that were maintained during the transition period between major versions.
Security professionals should note that this vulnerability aligns with CWE-400, which covers improper handling of resources that can lead to memory exhaustion and denial of service conditions. The flaw demonstrates poor resource management practices within the authentication subsystem where temporary database objects are not properly cleaned up during authentication failures against non-existent databases. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, making it a valuable target for attackers seeking to disrupt database services. The vulnerability's exploitation pattern makes it particularly effective in environments where MongoDB instances are exposed to untrusted networks or where authentication bypasses are possible.
Mitigation strategies for CVE-2016-3104 require immediate implementation of several defensive measures. Organizations should upgrade to MongoDB versions that address this specific authentication handling flaw, typically versions 2.6.12 or later, which contain fixes for the memory management issues in the authentication subsystem. Additionally, administrators should disable 2.4-style user authentication where possible, as this legacy feature creates multiple security vulnerabilities beyond this specific denial of service issue. Network segmentation and access control measures should be implemented to limit exposure of MongoDB instances to untrusted networks, while monitoring systems should be configured to detect unusual memory consumption patterns that may indicate exploitation attempts. Regular patch management processes should be established to ensure that all MongoDB instances receive timely security updates, particularly during transition periods when legacy features are maintained for compatibility purposes.