CVE-2018-15876 in ajax-bootmodal-login Plugin
Summary
by MITRE
An issue was discovered in the ajax-bootmodal-login plugin 1.4.3 for WordPress. The register form, login form, and password-recovery form require solving a CAPTCHA to perform actions. However, this is required only once per user session, and therefore one could send as many requests as one wished by automation.
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Analysis
by VulDB Data Team • 03/18/2020
The vulnerability identified as CVE-2018-15876 resides within the ajax-bootmodal-login plugin version 1.4.3 for WordPress platforms, representing a significant security weakness in user authentication mechanisms. This issue manifests through flawed CAPTCHA validation implementation that creates an exploitable condition in the plugin's authentication workflow. The vulnerability specifically affects the register form, login form, and password recovery form components, which are all designed to require CAPTCHA verification as a protective measure against automated abuse. However, the implementation contains a critical design flaw that undermines the intended security controls.
The technical flaw stems from the session-based CAPTCHA validation approach where users are only required to solve the CAPTCHA once per user session rather than for each individual action. This design decision creates a persistent vulnerability that allows malicious actors to bypass the intended rate limiting and anti-automation protections. The implementation follows a pattern that aligns with CWE-384, which addresses session management vulnerabilities where the security controls are insufficient to prevent automated attacks. Attackers can leverage this weakness by maintaining a single session and repeatedly submitting requests through automation tools, effectively circumventing the CAPTCHA protection mechanism that was designed to prevent abuse.
The operational impact of this vulnerability extends beyond simple account enumeration or brute force attacks, creating a comprehensive threat vector that can be exploited for various malicious activities. The ability to send unlimited requests through automation enables attackers to perform credential stuffing, account takeover attempts, and spam registration campaigns with minimal detection risk. This vulnerability directly maps to ATT&CK technique T1110, which covers credential access methods including password guessing and brute force attacks. The persistent nature of the session-based CAPTCHA bypass allows for sustained attack campaigns that can overwhelm system resources and potentially lead to account compromise at scale.
Mitigation strategies for this vulnerability should focus on implementing proper CAPTCHA validation for each individual action rather than per session. The recommended approach involves reworking the authentication flow to require CAPTCHA verification for every registration, login, and password recovery attempt, regardless of session state. Security measures should include implementing rate limiting mechanisms at the application level, enforcing stricter session management policies, and deploying additional validation checks that monitor for automated behavior patterns. Organizations should also consider implementing multi-factor authentication controls and monitoring for unusual request patterns that could indicate automated abuse attempts. The fix should align with industry best practices for session management and CAPTCHA implementation as outlined in OWASP authentication guidelines and NIST cybersecurity frameworks to ensure comprehensive protection against similar vulnerabilities.