CVE-2026-61630 in nginx-ignition
Summary
by MITRE • 09/21/2026
nginx ignition is a user interface for the nginx web server. In versions 2.33.0 through 2.35.0, any user that has enabled the OTP 2FA can have their TOTP reused during the standard 30 second validity window. Version 2.35.1 patches the issue.
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Analysis
by VulDB Data Team • 09/21/2026
The vulnerability identified in nginx ignition versions 2.33.0 through 2.35.0 represents a critical failure in the implementation of Two-Factor Authentication (2FA) mechanisms, specifically concerning Time-based One-Time Passwords or TOTP protocols. Nginx ignition serves as a user interface for managing the nginx web server, and its security posture is paramount given that it often controls access to sensitive infrastructure configurations. The flaw lies within the validation logic used during the authentication process when OTP 2FA is enabled by the end-user. Under normal operational parameters of TOTP systems, such as those defined in RFC 6238, a generated code is valid for a limited time window, typically thirty seconds, to mitigate replay attacks and reduce the risk of interception. However, within this specific version range, the application fails to properly invalidate or track the usage status of these codes during that validity period.
This technical flaw allows an attacker who has obtained or intercepted a valid TOTP code to reuse it multiple times before the thirty-second window expires. In a secure implementation, once a TOTP is successfully used for authentication, the system should immediately mark it as consumed and reject any subsequent attempts using the same token value within that time frame. The absence of this state management means that if an attacker can capture the initial valid code through network sniffing, side-channel attacks, or other interception methods, they are not limited to a single use attempt. They can replay the exact same credential string repeatedly until either the thirty-second window closes or another user successfully consumes it first. This significantly lowers the barrier for unauthorized access compared to standard TOTP implementations where each code is strictly one-time use.
From an operational impact perspective, this vulnerability undermines the primary security benefit of two-factor authentication: the assumption that possession of a second factor provides dynamic, unique proof of identity. By allowing reuse within the validity window, the system effectively degrades 2FA to something resembling static password protection with a short expiration time, rather than true multi-factor verification. An attacker in position to observe network traffic or exploit local session vulnerabilities can bypass authentication controls entirely if they act quickly enough within that thirty-second frame. This poses severe risks for administrative accounts and any users relying on nginx ignition for secure server management, potentially leading to unauthorized configuration changes, data exfiltration, or further compromise of the underlying infrastructure.
The vulnerability aligns with CWE-294, which describes a security flaw related to authentication bypass due to acceptance of a replayed message. Furthermore, in the context of the MITRE ATT&CK framework, this behavior facilitates techniques associated with Credential Replay and potentially Account Manipulation if an attacker gains persistent access through repeated successful authentications before detection mechanisms can trigger alerts for anomalous login patterns. The lack of immediate invalidation also complicates forensic analysis as multiple log entries may appear identical from a credential perspective despite occurring at different seconds within the window, making it harder to distinguish between legitimate rapid retries and malicious replay attacks without additional session state tracking.
To mitigate this risk, organizations running nginx ignition versions 2.33.0 through 2.35.0 must upgrade immediately to version 2.35.1 or later, where the patch addresses the failure in TOTP validation logic by ensuring that once a code is accepted for authentication, it is permanently invalidated within its validity window regardless of subsequent requests. Until an upgrade can be performed, administrators should consider implementing network-level controls such as strict rate limiting on login endpoints to reduce the likelihood of successful replay attacks during the thirty-second window. Additionally, enabling comprehensive logging and monitoring for multiple rapid authentication attempts from a single source IP address or user account can help detect potential exploitation activities in real-time. It is also advisable to review access logs for any signs of repeated use of identical TOTP values within short timeframes as an indicator of compromise while the patching process is underway.