CVE-2021-37627 in Contao
Summary
by MITRE • 08/12/2021
Contao is an open source CMS that allows creation of websites and scalable web applications. In affected versions it is possible to gain privileged rights in the Contao back end. Installations are only affected if they have untrusted back end users who have access to the form generator. All users are advised to update to Contao 4.4.56, 4.9.18 or 4.11.7. As a workaround users may disable the form generator or disable the login for untrusted back end users.
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Analysis
by VulDB Data Team • 08/17/2021
CVE-2021-37627 represents a critical privilege escalation vulnerability within the Contao content management system that undermines the security boundaries of the back end interface. This vulnerability specifically targets installations where untrusted back end users possess access to the form generator component, creating a pathway for attackers to elevate their privileges and gain administrative control over the CMS. The flaw exists in the authorization mechanisms that govern user permissions within the Contao platform, allowing malicious actors with limited access to exploit a design weakness in the form handling functionality. The vulnerability is categorized under CWE-284, which addresses improper access control issues in software systems, and aligns with ATT&CK techniques related to privilege escalation through application vulnerabilities.
The technical implementation of this vulnerability stems from insufficient validation of user permissions when processing form submissions within the Contao back end. When untrusted users interact with the form generator, the system fails to properly verify whether these users possess the necessary administrative privileges to perform actions that should be restricted to authorized administrators. This misconfiguration allows attackers to manipulate form data or submission processes in ways that bypass normal access controls. The attack vector specifically requires that the target installation has untrusted back end users with form generator access, making the vulnerability exploitable only in environments where such user roles exist. The flaw demonstrates poor input validation and insufficient authorization checks that are fundamental security principles in secure application design.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with comprehensive administrative access to the Contao installation. Once successfully exploited, attackers can modify website content, add malicious code, compromise user data, and potentially use the compromised system as a foothold for further attacks within the network infrastructure. The vulnerability affects all versions prior to the patched releases, creating a significant risk for organizations that have not yet applied the necessary updates. This type of vulnerability is particularly dangerous in web application environments where CMS platforms serve as central management interfaces for multiple websites and applications, as it allows attackers to gain persistent access to critical business infrastructure.
Organizations affected by CVE-2021-37627 must prioritize immediate remediation through the recommended software updates to Contao versions 4.4.56, 4.9.18, or 4.11.7, which contain the necessary patches to address the privilege escalation flaw. The workaround solutions provided by the vendor offer temporary mitigation strategies that can be implemented while awaiting the official updates, including disabling the form generator functionality or removing login access for untrusted users. Security teams should conduct comprehensive assessments of their Contao installations to identify all instances where untrusted users have access to back end components, particularly those with form generator capabilities. Additionally, organizations should implement monitoring solutions to detect unusual activity patterns that might indicate exploitation attempts, as this vulnerability could be targeted by automated attack tools seeking to compromise CMS platforms. The vulnerability highlights the importance of maintaining current security patches and implementing proper user access controls in web application environments.