CVE-2023-36830 in SQLFluff
Summary
by MITRE • 07/06/2023
SQLFluff is a SQL linter. Prior to version 2.1.2, in environments where untrusted users have access to the config files, there is a potential security vulnerability where those users could use the `library_path` config value to allow arbitrary python code to be executed via macros. For many users who use SQLFluff in the context of an environment where all users already have fairly escalated privileges, this may not be an issue - however in larger user bases, or where SQLFluff is bundled into another tool where developers still wish to give users access to supply their on rule configuration, this may be an issue.
The 2.1.2 release offers the ability for the `library_path` argument to be overwritten on the command line by using the `--library-path` option. This overrides any values provided in the config files and effectively prevents this route of attack for users which have access to the config file, but not to the scripts which call the SQLFluff CLI directly. A similar option is provided for the Python API, where users also have a greater ability to further customise or override configuration as necessary. Unless `library_path` is explicitly required, SQLFluff maintainers recommend using the option `--library-path none` when invoking SQLFluff which will disable the `library-path` option entirely regardless of the options set in the configuration file or via inline config directives. As a workaround, limiting access to - or otherwise validating configuration files before they are ingested by SQLFluff will provides a similar effect and does not require upgrade.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/25/2023
CVE-2023-36830 represents a critical security vulnerability within SQLFluff, a popular SQL linter tool, that exposes systems to arbitrary code execution through improper configuration handling. This vulnerability exists in versions prior to 2.1.2 and specifically targets environments where untrusted users can access configuration files, creating a potential attack vector through the `library_path` configuration parameter. The flaw allows malicious actors to inject and execute arbitrary Python code via macros, leveraging the tool's ability to load external libraries through configuration settings. This represents a classic privilege escalation vulnerability where user-controlled configuration values can be manipulated to execute unauthorized code within the context of the SQLFluff process.
The technical implementation of this vulnerability stems from SQLFluff's handling of the `library_path` configuration value, which is designed to allow users to specify additional Python modules for custom rule implementations. However, the vulnerability occurs when the tool processes user-supplied configuration files without proper sanitization or validation of the library path values. When untrusted users can modify configuration files, they can specify malicious Python paths that will be executed during SQLFluff's macro processing, effectively bypassing normal security boundaries. This type of vulnerability aligns with CWE-472 Unprotected Primary Resource and CWE-94 Improper Control of Generation of Code, as it allows attackers to manipulate code generation through external inputs.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete system compromise when SQLFluff is deployed in multi-user environments or integrated into larger applications where users should not have elevated privileges. In enterprise settings where SQLFluff is bundled into development tools or CI/CD pipelines, this vulnerability could allow attackers to execute malicious code on build servers, data processing systems, or other critical infrastructure. The vulnerability is particularly concerning because it can be exploited through configuration files that users might legitimately modify for legitimate purposes, making detection and prevention more challenging. Attackers could potentially use this to establish persistent backdoors, exfiltrate data, or perform other malicious activities within the compromised environment.
The fix implemented in version 2.1.2 addresses this vulnerability through multiple mitigation strategies that align with security best practices. The introduction of the `--library-path` command-line option provides administrators with a mechanism to override configuration file values, effectively preventing the exploitation route when users can modify config files but not execute scripts directly. Additionally, the Python API now includes similar override capabilities, ensuring comprehensive protection across all usage contexts. The recommendation to use `--library-path none` when invoking SQLFluff provides a simple yet effective defense mechanism that completely disables the library path functionality regardless of configuration settings. This approach follows the principle of least privilege and aligns with ATT&CK technique T1059.006 Command and Scripting Interpreter: Python, where attackers often attempt to leverage legitimate interpreter capabilities for malicious purposes. Organizations can also implement access controls and configuration validation as workarounds, which directly addresses the need for input validation and privilege separation as outlined in security frameworks such as the OWASP Top Ten and NIST cybersecurity guidelines. The vulnerability demonstrates the importance of validating all user inputs and avoiding the execution of untrusted code, particularly in tools that are designed to process and analyze user-provided data.