CVE-2026-100508 in Two Factor Plugin
Summary
by MITRE • 09/30/2026
Unauthenticated Denial of Service Attack in Two Factor <= 0.16.0 versions.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified as an unauthenticated denial of service attack within the Two Factor plugin for versions up to and including 0.16.0 represents a critical availability risk for web applications relying on this authentication mechanism. This flaw allows any remote, unauthenticated attacker to disrupt the normal functioning of the targeted system without requiring valid credentials or prior interaction with the application's secure areas. The core technical issue stems from insufficient input validation and resource management controls within the plugin’s handling of multi-factor authentication requests. Specifically, the code fails to properly limit the rate at which verification codes can be requested or validated, nor does it implement adequate safeguards against automated scripting tools designed to flood the system with repetitive authentication attempts. This lack of throttling mechanisms means that an attacker can generate a high volume of legitimate-looking but maliciously timed requests aimed at exhausting server resources such as CPU cycles, memory allocation, or database connection pools associated with generating and verifying time-based one-time passwords or SMS codes.
From a technical perspective, this vulnerability aligns closely with CWE-400, which describes uncontrolled resource consumption leading to denial of service conditions. The attacker exploits the computational overhead required by the Two Factor plugin to process each authentication attempt. By sending a rapid succession of requests, often using simple automated scripts or botnets, the server becomes overwhelmed trying to generate unique codes, validate inputs against stored hashes, and manage session states for non-existent users. This resource exhaustion prevents legitimate users from logging in, effectively rendering the application unusable during the attack window. The severity is compounded by the fact that no authentication is required, lowering the barrier to entry significantly and allowing any individual on the internet with basic networking knowledge to execute this denial of service vector against vulnerable installations.
The operational impact of this vulnerability extends beyond simple downtime; it can lead to significant financial loss due to lost productivity and revenue during outages, as well as reputational damage if customers perceive the platform as unreliable or insecure. Furthermore, such vulnerabilities are often used as a distraction technique by attackers who may simultaneously attempt other malicious activities while system administrators are focused on mitigating the denial of service symptoms. In terms of threat modeling, this behavior is consistent with ATT&CK tactic TA0004 Impact and specifically relates to techniques that disrupt availability, although it does not fit neatly into standard persistence or privilege escalation categories since its primary goal is disruption rather than control. The lack of authentication requirement places it in the initial access phase as a vector for causing harm without needing foothold privileges first.
Mitigation strategies must focus on implementing robust rate limiting and input validation controls at both the application layer and infrastructure level. Administrators should immediately update the Two Factor plugin to version 0.16.1 or later, where these resource management flaws have been addressed by developers through improved throttling logic that limits the number of authentication requests per user IP address within a specific time frame. Additionally, deploying web application firewalls can help mitigate this risk by detecting and blocking abnormal traffic patterns characteristic of denial of service attacks before they reach the vulnerable application code. It is also advisable to implement CAPTCHA challenges after a small threshold of failed login attempts to deter automated scripting tools from flooding the system. Regular security audits and penetration testing should be conducted to identify similar resource exhaustion vulnerabilities in other components of the web stack, ensuring that availability controls are comprehensive across all user-facing endpoints.