CVE-2022-34028 in NJS
Summary
by MITRE • 07/19/2022
Nginx NJS v0.7.5 was discovered to contain a segmentation violation via njs_utf8_next at src/njs_utf8.h.
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Analysis
by VulDB Data Team • 08/06/2022
The vulnerability identified as CVE-2022-34028 affects Nginx NJS version 0.7.5 and represents a critical segmentation fault condition within the UTF-8 processing functionality of the Nginx JavaScript engine. This flaw manifests specifically within the njs_utf8_next function located in the src/njs_utf8.h source file, where improper handling of UTF-8 encoded input data can lead to memory access violations and potential system instability. The issue arises from inadequate bounds checking and validation during UTF-8 character processing operations, creating a pathway for maliciously crafted input to trigger unauthorized memory access patterns that result in segmentation violations.
The technical exploitation of this vulnerability occurs when Nginx processes HTTP requests containing specially crafted UTF-8 encoded data through its JavaScript processing capabilities. The njs_utf8_next function fails to properly validate input boundaries when parsing UTF-8 multibyte sequences, allowing attackers to manipulate memory pointers and cause the application to attempt accessing invalid memory locations. This type of vulnerability falls under the CWE-125 vulnerability category, which specifically addresses out-of-bounds read conditions, and represents a classic example of memory safety issues that can lead to arbitrary code execution or denial of service scenarios. The flaw demonstrates characteristics consistent with the ATT&CK technique T1203, where adversaries may leverage memory corruption vulnerabilities to gain control over system resources.
From an operational impact perspective, this vulnerability poses significant risks to web servers utilizing Nginx with JavaScript processing capabilities, particularly in environments where user input is processed through the NJS engine. The segmentation fault can result in immediate service disruption through process crashes, leading to denial of service conditions that affect legitimate users. Additionally, the vulnerability could potentially be exploited in combination with other techniques to achieve remote code execution, especially in scenarios where the affected Nginx instances are configured to process untrusted input through JavaScript modules. The risk is amplified in web applications that rely heavily on dynamic content generation and user interaction processing, as these environments provide more opportunities for exploitation through crafted HTTP requests containing malformed UTF-8 sequences.
Mitigation strategies for CVE-2022-34028 should prioritize immediate patching of affected Nginx NJS installations to version 0.7.6 or later, which contains the necessary fixes for the UTF-8 processing functions. Organizations should also implement input validation measures that sanitize all user-provided data before processing through JavaScript engines, reducing the attack surface for potential exploitation. Network-level protections including web application firewalls and intrusion detection systems can provide additional layers of defense by monitoring for suspicious UTF-8 sequences and malformed requests that may indicate exploitation attempts. Security teams should conduct comprehensive vulnerability assessments across all Nginx installations to identify systems running affected versions and establish monitoring procedures to detect potential exploitation attempts. The remediation process should include thorough testing of patched environments to ensure that the fix does not introduce regressions in legitimate functionality while maintaining the security posture against this specific segmentation violation vulnerability.