CVE-2026-107805 in Nginx UI
Summary
by MITRE • 10/09/2026
Nginx UI is a web user interface for the Nginx web server. From 2.5.0 until 2.6.0, the node-signature authentication path performs temporary file staging of an attacker-controlled request body and synchronizes it before validating the body digest and cryptographic signature. An unauthenticated remote client that can reach the API and provide syntactically valid signature metadata can consume temporary filesystem capacity, disk input and output, and request-processing resources before rejection. The issue affects availability and does not bypass authentication or provide confidentiality or integrity impact. This issue is fixed in version 2.6.0.
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Analysis
by VulDB Data Team • 10/09/2026
The vulnerability identified within Nginx UI versions ranging from 2.5.0 to 2.6.0 represents a significant resource exhaustion flaw located specifically within the node-signature authentication path of the application's API interface. This web-based management tool for the Nginx reverse proxy server processes incoming requests by first staging the request body into a temporary file on the local filesystem before proceeding with cryptographic validation steps. The core technical deficiency lies in the order of operations performed during this authentication sequence, where the system commits substantial I/O resources and disk space to handle potentially large payloads prior to verifying whether those payloads are legitimate or authorized.
From an operational perspective, this architectural decision creates a window of opportunity for unauthenticated remote attackers who possess network access to the API endpoint. By submitting requests with syntactically valid signature metadata but containing maliciously crafted bodies, an attacker can trigger the temporary file creation and synchronization processes repeatedly. This behavior leads to rapid consumption of available disk space on the server hosting Nginx UI, excessive input and output operations that degrade system performance, and increased CPU usage due to unnecessary processing overhead. The cumulative effect is a denial-of-service condition where legitimate administrative functions may become sluggish or entirely unavailable as resources are depleted by these malicious requests.
The impact of this vulnerability is strictly limited to availability, meaning it does not compromise the confidentiality of sensitive configuration data nor does it affect the integrity of stored information. Furthermore, because the attack relies on syntactically valid metadata but fails at later validation stages, it does not bypass authentication mechanisms in a way that grants unauthorized access or privilege escalation. The attacker cannot read protected data or modify server configurations through this specific vector; instead, they can only disrupt service availability by exhausting system resources. This distinction is critical for risk assessment, as the threat model focuses on operational disruption rather than direct compromise of the underlying Nginx infrastructure or its configuration files.
This flaw aligns with Common Weakness Enumeration category CWE-400, which covers uncontrolled resource consumption, and specifically relates to issues where input validation occurs after significant processing has already begun. In terms of adversary tactics, this behavior mirrors techniques found in MITRE ATT&CK frameworks related to Resource Hijacking or Denial of Service via application layer exhaustion, particularly when targeting web services that process large payloads without prior size limits or authentication checks. The vulnerability highlights the importance of implementing strict input validation and resource limiting strategies before engaging in expensive operations such as disk I/O for temporary file staging.
The recommended mitigation strategy involves upgrading to Nginx UI version 2.6.0, where this issue has been resolved by reordering the processing logic to validate signatures and digests prior to allocating filesystem resources. For environments that cannot immediately upgrade, administrators should implement network-level controls such as rate limiting on the API endpoints to restrict the frequency of authentication requests from single sources. Additionally, configuring web server proxies or load balancers in front of Nginx UI to enforce strict body size limits can prevent attackers from submitting excessively large payloads that trigger the resource exhaustion flaw. Monitoring disk usage and I/O metrics for anomalous spikes associated with API traffic can also serve as an effective detection mechanism for ongoing exploitation attempts until a permanent patch is applied.