CVE-2021-29047 in Liferay
Summary
by MITRE • 05/16/2021
The SimpleCaptcha implementation in Liferay Portal 7.3.4, 7.3.5 and Liferay DXP 7.3 before fix pack 1 does not invalidate CAPTCHA answers after it is used, which allows remote attackers to repeatedly perform actions protected by a CAPTCHA challenge by reusing the same CAPTCHA answer.
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Analysis
by VulDB Data Team • 05/20/2021
The vulnerability identified as CVE-2021-29047 represents a critical security flaw in the SimpleCaptcha implementation within Liferay Portal versions 7.3.4 and 7.3.5, as well as Liferay DXP 7.3 prior to fix pack 1. This issue stems from a fundamental design flaw in how CAPTCHA validation is handled, specifically the failure to invalidate CAPTCHA answers after their initial use. The vulnerability operates at the application logic level, where the system maintains the validity of CAPTCHA responses beyond their intended single-use context, creating a persistent security weakness that undermines the core purpose of CAPTCHA mechanisms.
The technical implementation flaw manifests as a lack of state management for CAPTCHA tokens within the Liferay Portal authentication and validation framework. When a user successfully completes a CAPTCHA challenge, the system should immediately invalidate that specific CAPTCHA answer to prevent reuse. However, the vulnerable implementation fails to perform this crucial invalidation step, allowing attackers to capture a valid CAPTCHA response and reuse it multiple times to bypass the protection mechanism. This vulnerability directly maps to CWE-384, which addresses the issue of session management flaws where authentication tokens are not properly invalidated after use, and aligns with ATT&CK technique T1110.003 for credential stuffing attacks that exploit reused authentication tokens.
The operational impact of this vulnerability is significant for organizations utilizing Liferay Portal, as it enables remote attackers to circumvent automated protection mechanisms designed to prevent abuse of web forms, registration processes, and other user-facing interfaces. Attackers can exploit this weakness to perform repeated actions such as account registration, password reset requests, comment submissions, and other CAPTCHA-protected operations without additional authentication challenges. This creates opportunities for spamming, account enumeration, and denial of service attacks against legitimate users, while potentially enabling more sophisticated attacks that rely on bypassing rate limiting and other security controls. The vulnerability affects the integrity of the authentication and authorization framework, undermining the trust model of the portal system.
Organizations affected by this vulnerability should immediately apply the available fix pack 1 for Liferay DXP 7.3 or upgrade to a patched version of Liferay Portal 7.3.4 and 7.3.5. System administrators should also implement additional monitoring for unusual patterns of CAPTCHA usage and consider implementing supplementary rate limiting controls to mitigate potential exploitation. The fix addresses the root cause by ensuring proper invalidation of CAPTCHA tokens upon first use, thereby restoring the intended security properties of the CAPTCHA mechanism. Security teams should conduct thorough vulnerability assessments to identify any other components within their Liferay deployments that might be susceptible to similar state management issues, particularly those involving authentication token handling and session management functions.