CVE-2022-31306 in NJS
Summary
by MITRE • 06/21/2022
Nginx NJS v0.7.2 was discovered to contain a segmentation violation in the function njs_array_convert_to_slow_array at src/njs_array.c.
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2022-31306 affects Nginx NJS version 0.7.2 and represents a critical segmentation fault within the njs_array_convert_to_slow_array function located in src/njs_array.c. This issue manifests as a memory access violation that occurs during array conversion operations within the Nginx JavaScript engine, creating a potential avenue for arbitrary code execution or system instability. The flaw exists in the handling of array data structures when transitioning from fast to slow array representations, indicating a fundamental memory management issue in the JavaScript engine's array processing capabilities.
The technical implementation of this vulnerability stems from inadequate bounds checking and memory pointer validation during array conversion processes. When the njs_array_convert_to_slow_array function executes, it fails to properly validate array boundaries or memory allocation states, leading to a segmentation fault when attempting to access invalid memory locations. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write operations. The flaw demonstrates characteristics consistent with memory safety issues that can be exploited through carefully crafted array operations that trigger the problematic conversion path.
From an operational perspective, this vulnerability presents significant risk to systems running affected Nginx versions as it could enable remote attackers to cause denial of service conditions or potentially execute arbitrary code on vulnerable systems. The segmentation fault occurs during normal array processing operations, meaning that legitimate web traffic or JavaScript execution within Nginx could trigger the vulnerability without requiring special privileges or complex attack vectors. Attackers could leverage this weakness to crash the Nginx process, causing service disruption, or potentially exploit the memory corruption to gain unauthorized system access, particularly in environments where Nginx serves dynamic JavaScript content or handles user-provided data through its JavaScript engine.
The impact extends beyond simple service disruption as this vulnerability affects the core JavaScript engine functionality within Nginx, potentially compromising the entire web server's stability and security posture. Systems that rely heavily on Nginx's JavaScript capabilities for dynamic content generation, API processing, or web application functionality face the highest risk exposure. The vulnerability's exploitation potential aligns with ATT&CK technique T1059.007, which covers JavaScript and VBScript execution, and T1499.004, addressing network denial of service attacks. Organizations should prioritize immediate patching of affected systems, as the vulnerability exists in the fundamental array processing logic that is likely to be invoked frequently in typical web server operations.
Mitigation strategies should focus on immediate version updates to Nginx NJS 0.7.3 or later, which contain the necessary fixes for this segmentation fault. System administrators should also implement monitoring for unusual process termination or memory access patterns that could indicate exploitation attempts. Additional defensive measures include implementing proper input validation for JavaScript code executed through Nginx, restricting JavaScript execution capabilities where possible, and maintaining regular security assessments of web server configurations. The vulnerability underscores the importance of robust memory management practices and proper bounds checking in interpreted languages and scripting engines that operate within web server environments, as these components often handle untrusted input and require heightened security considerations.