CVE-2021-29481 in Ratpack
Summary
by MITRE • 06/30/2021
Ratpack is a toolkit for creating web applications. In versions prior to 1.9.0, the default configuration of client side sessions results in unencrypted, but signed, data being set as cookie values. This means that if something sensitive goes into the session, it could be read by something with access to the cookies. For this to be a vulnerability, some kind of sensitive data would need to be stored in the session and the session cookie would have to leak. For example, the cookies are not configured with httpOnly and an adjacent XSS vulnerability within the site allowed capture of the cookies. As of version 1.9.0, a securely randomly generated signing key is used. As a workaround, one may supply an encryption key, as per the documentation recommendation.
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Analysis
by VulDB Data Team • 07/04/2021
CVE-2021-29481 represents a session management vulnerability in the Ratpack web application toolkit affecting versions prior to 1.9.0. This flaw stems from the default configuration where client-side sessions are stored as cookie values that are signed but not encrypted, creating a significant security risk when sensitive data is stored within these sessions. The vulnerability operates under CWE-312, which specifically addresses the exposure of sensitive information through improper handling of data that should remain confidential. The technical implementation involves the use of signed session cookies that contain session data in plaintext format, making them susceptible to unauthorized reading when accessed by malicious actors who can intercept these cookies.
The operational impact of this vulnerability becomes apparent when considering the typical attack vectors that could exploit such a flaw. An attacker with access to session cookies could potentially extract sensitive information that was stored within the application's session management system. This risk is particularly pronounced when combined with other vulnerabilities such as cross-site scripting attacks, where an adjacent XSS vulnerability could allow capture of session cookies from a victim's browser. The absence of the httpOnly flag on cookies further exacerbates the situation by making them accessible to client-side scripts, thus providing attackers with multiple pathways to exploit the vulnerable session storage mechanism. This vulnerability aligns with ATT&CK technique T1531, which focuses on "Modify System Firmware", though in this case the modification occurs through session cookie manipulation rather than firmware changes.
The security implications extend beyond simple information disclosure, as the signed nature of the cookies does not prevent data reading but rather provides authentication of the cookie's origin. Attackers could potentially manipulate session data even if they cannot directly modify the signing mechanism, leading to session hijacking or privilege escalation scenarios. The fix implemented in version 1.9.0 addresses this by introducing a securely randomly generated signing key, which significantly improves the security posture of applications using Ratpack. However, organizations should also consider implementing additional mitigations such as explicitly configuring encryption keys as recommended in the documentation, ensuring cookies are properly configured with security flags, and implementing comprehensive session management policies that limit the amount of sensitive data stored in sessions.
The vulnerability demonstrates the importance of proper session management practices and highlights how seemingly minor configuration defaults can create significant security risks in web applications. Organizations using Ratpack should perform immediate upgrades to version 1.9.0 or later, while also conducting thorough security reviews of their session management implementations to ensure no sensitive data is unnecessarily stored in client-side sessions. The remediation process should include verification that session cookies are properly configured with httpOnly and secure flags, and that applications do not store sensitive information in session data that could be exposed through cookie interception. This vulnerability serves as a reminder of the critical nature of secure default configurations and the potential for seemingly benign session management features to become attack vectors when not properly secured.