CVE-2021-3779 in ruby-mysql
Summary
by MITRE • 06/28/2022
A malicious MySQL server can request local file content from a client using ruby-mysql prior to version 2.10.0 without explicit authorization from the user. This issue was resolved in version 2.10.0 and later.
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Analysis
by VulDB Data Team • 07/16/2022
The vulnerability identified as CVE-2021-3779 represents a significant security flaw in the ruby-mysql gem, which is a client library used for connecting to mysql databases from ruby applications. This issue allows a malicious mysql server to potentially access local files on the client system without explicit user authorization, creating a dangerous privilege escalation scenario that could lead to data exfiltration or system compromise.
The technical flaw stems from improper handling of file access requests within the ruby-mysql client library. When a client connects to a mysql server, the library should validate and authorize any requests for local file operations. However, versions prior to 2.10.0 failed to implement proper access controls, enabling a malicious server to craft specific requests that would cause the client library to read and return local file contents to the attacker. This behavior violates fundamental security principles of client-server communication and demonstrates a failure in input validation and access control mechanisms.
The operational impact of this vulnerability extends beyond simple data leakage, as it can enable attackers to extract sensitive information such as configuration files, database credentials, application source code, and other locally stored data. The vulnerability is particularly concerning because it operates at the client library level, meaning that any ruby application using the affected version of ruby-mysql could be compromised simply by connecting to a malicious mysql server. This creates a wide attack surface and makes the vulnerability particularly dangerous in environments where applications connect to untrusted or compromised database servers.
This vulnerability aligns with CWE-250, which describes "Execute Code from Untrusted Control Source," and represents a classic case of insecure direct object reference where the client library fails to properly validate file access requests. The issue also maps to ATT&CK technique T1071.004, which covers application layer protocol traffic, as the malicious server exploits the mysql protocol to perform unauthorized file access. Organizations using ruby applications that connect to mysql databases should immediately update their ruby-mysql gem to version 2.10.0 or later to mitigate this risk.
The fix implemented in ruby-mysql version 2.10.0 includes enhanced input validation and stricter access controls for file operations, ensuring that local file access requests are properly authenticated and authorized. Security teams should conduct comprehensive audits of their ruby application environments to identify all systems using vulnerable versions of the gem, and implement monitoring to detect potential exploitation attempts. Additionally, network segmentation and database access controls should be reviewed to minimize the impact of potential compromise, as the vulnerability could be leveraged to gain access to sensitive system information that might otherwise be protected by traditional network security measures.