CVE-2022-3638 in Nginx
Summary
by MITRE • 10/21/2022
A vulnerability was found in Nginx and classified as problematic. This issue affects some unknown processing of the file ngx_resolver.c of the component IPv4 Off Handler. The manipulation leads to memory leak. The attack may be initiated remotely. It is recommended to apply a patch to fix this issue. The identifier VDB-211937 was assigned to this vulnerability.
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Analysis
by VulDB Data Team • 07/24/2026
The vulnerability identified in Nginx represents a critical memory leak condition within the resolver component that specifically impacts the IPv4 off handler functionality. This flaw resides in the ngx_resolver.c file, which governs how Nginx processes DNS resolution requests and handles IPv4 address lookups. The memory leak occurs during the normal processing flow of DNS queries, where allocated memory structures fail to be properly released back to the system after completing their intended function. This particular vulnerability demonstrates a classic pattern of resource management failure that can escalate into system instability when exploited over time.
The technical execution of this memory leak vulnerability requires remote exploitation through network-based attack vectors that leverage the resolver functionality within Nginx's configuration. Attackers can trigger the flaw by sending specially crafted DNS requests or by manipulating the IPv4 off handler during normal HTTP request processing. The memory consumption grows progressively with each affected request, leading to potential denial of service conditions where the server eventually exhausts available memory resources and becomes unresponsive to legitimate traffic. This type of vulnerability aligns with CWE-401, which specifically addresses improper handling of memory allocation and deallocation in software systems.
From an operational impact perspective, this vulnerability presents significant risks to web server availability and system stability. The progressive nature of the memory leak means that servers running affected Nginx versions will gradually consume increasing amounts of system resources until they either crash or become unresponsive to legitimate client requests. Network administrators may experience unexpected service interruptions, increased system monitoring alerts, and potential security incidents where the server becomes unavailable during critical business hours. The remote exploitability of this flaw makes it particularly dangerous as attackers can initiate attacks without requiring physical access to the target system.
Security professionals should prioritize immediate patching of affected Nginx installations to prevent exploitation of this memory leak vulnerability. The recommended mitigation strategy involves upgrading to the latest stable Nginx version that contains the fixed resolver.c implementation with proper memory management routines. Additionally, implementing network monitoring solutions that track memory consumption patterns and setting up automated alerts for unusual resource usage can help detect exploitation attempts before they cause significant service disruption. Organizations should also consider implementing rate limiting mechanisms on DNS resolution requests to reduce the impact of potential abuse while awaiting official patches. This vulnerability exemplifies the importance of maintaining current security patches and following established cybersecurity frameworks such as those outlined in the ATT&CK framework for preventing remote code execution through resource management flaws.