Authentication Bypass via TOTP Reuse in nginx Ignition

Executive Summary

CVE-2026-61630 is a vulnerability in nginx-ignition versions 2.33.0 through 2.35.0 where Time-based One-Time Passwords (TOTP) used for two-factor authentication (2FA) can be reused within the standard 30-second validity window. This occurs because the application does not enforce checks to prevent TOTP reuse, violating OWASP ASVS recommendations that TOTPs should only be usable once.

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Detection Guidance

Check if your nginx-ignition instance is running versions 2.33.0 through 2.35.0. Use commands like 'nginx-ignition --version' or inspect package metadata. Monitor authentication logs for repeated TOTP attempts within the 30-second window.

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Impact Analysis

If an attacker intercepts a valid TOTP code during the 30-second window, they could reuse it to gain unauthorized access to the account. This undermines the security of 2FA, increasing the risk of account compromise through phishing or network capture. The attack requires high privileges and user interaction, making it less likely but still a serious concern.

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Compliance Impact

This vulnerability may violate compliance requirements for strong authentication mechanisms, such as those outlined in GDPR and HIPAA, which mandate robust security controls. Failure to enforce single-use TOTPs could result in non-compliance with data protection standards, potentially leading to legal and regulatory penalties.

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Mitigation Strategies

Upgrade to nginx-ignition version 2.35.1 or later immediately. Implement application-level tracking to prevent TOTP reuse within the validity window. Review and enhance logging for authentication attempts.

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