CVE-2022-27007 in njs
Summary
by MITRE • 04/14/2022
nginx njs 0.7.2 is affected suffers from Use-after-free in njs_function_frame_alloc() when it try to invoke from a restored frame saved with njs_function_frame_save().
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Analysis
by VulDB Data Team • 04/20/2022
The vulnerability identified as CVE-2022-27007 affects nginx njs version 0.7.2 and represents a critical use-after-free condition within the njs_function_frame_alloc() function. This flaw occurs during the execution of JavaScript code within the nginx environment where the njs engine manages function call frames. The vulnerability specifically manifests when attempting to invoke functions that were previously saved using the njs_function_frame_save() mechanism, creating a scenario where memory that has been freed is subsequently accessed, leading to potential arbitrary code execution or system instability.
The technical implementation of this vulnerability stems from improper memory management within the njs JavaScript engine's frame allocation system. When the njs_function_frame_save() function stores the state of a function frame for later restoration, it creates a snapshot of the execution context. However, the njs_function_frame_alloc() function fails to properly validate the memory state when restoring these saved frames, resulting in a situation where freed memory locations are accessed during function invocation. This memory corruption vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software systems. The flaw demonstrates a classic memory safety issue where the application attempts to reference memory that has already been deallocated, potentially allowing attackers to manipulate program execution flow.
The operational impact of CVE-2022-27007 is significant within nginx environments that utilize the njs JavaScript engine for dynamic content processing, module extensions, or server-side scripting capabilities. Attackers could exploit this vulnerability by crafting malicious JavaScript code that triggers the specific sequence of frame saving and restoration operations, potentially leading to remote code execution on the affected nginx server. The vulnerability affects systems where nginx is configured to execute JavaScript through njs, particularly those running version 0.7.2 or earlier. This could compromise web servers, proxy configurations, or API gateways that rely on njs for dynamic request handling, content generation, or server-side logic execution.
Mitigation strategies for this vulnerability primarily focus on immediate version updates to nginx njs 0.7.3 or later, which contains the necessary patches to address the memory management issue in frame allocation. System administrators should prioritize updating their nginx installations to ensure the patched version resolves the use-after-free condition. Additionally, implementing network segmentation and access controls can help limit the potential impact of exploitation attempts. Monitoring for suspicious JavaScript execution patterns and implementing robust input validation for dynamic content processing can provide additional defensive layers. Organizations should also consider implementing the principle of least privilege for nginx processes and regularly review their JavaScript-based configurations to minimize the attack surface. The vulnerability demonstrates the importance of memory safety in interpreted languages within web server contexts, aligning with ATT&CK technique T1059.007 for scripting languages and T1211 for exploitation of memory corruption vulnerabilities.