NGINX is a powerful open-source web server that is widely used by large organizations and websites to manage their online presence. With its modular architecture, NGINX allows developers to extend its functionality by writing custom modules. While this makes NGINX extremely flexible and customizable, it also introduces a potential security risk if the modules are not designed and implemented with security in mind.
Recently, researchers at the ISAB Engineering Team discovered a vulnerability in the NGINX module system that could be exploited by attackers to execute arbitrary code. The vulnerability lies in the way that modules are defined and initialized within NGINX.
Specifically, the vulnerability occurs when a module fails to properly initialize a structure that is used to store module-specific configuration settings. Attackers can exploit this vulnerability by crafting a specially-crafted request that triggers the uninitialized structure to be used, causing a memory leak or other type of memory corruption.
To demonstrate this vulnerability, the ISAB Engineering Team has provided an example of a vulnerable NGINX module. The module, called
ngx_http_rofl_module, contains a structure of type
ngx_module_t that is used to store module-specific configuration settings. In this module, the structure is not properly initialized, leaving it vulnerable to exploitation.
To exploit this vulnerability, an attacker would need to craft a specially-crafted request that triggers the uninitialized structure to be used. This could be done, for example, by sending a request that contains a carefully-crafted payload that overwrites the uninitialized structure with arbitrary data.
To mitigate this vulnerability, NGINX module developers should ensure that any structures used to store module-specific configuration settings are properly initialized before use. Additionally, NGINX users should be sure to keep their installations up-to-date with the latest security patches.
NGINX has released a security advisory addressing this vulnerability, which can be found here. We strongly recommend that all NGINX users review this advisory and take appropriate action to mitigate the vulnerability.
In conclusion, while the modular architecture of NGINX allows for incredible flexibility and customization, it also introduces potential security risks if the modules are not designed and implemented with security in mind. The ISAB Engineering Team is committed to helping organizations identify and mitigate these risks, and we encourage all NGINX users to take steps to secure their installations.