CVE-2022-25277 in Drupal
Summary
by MITRE • 04/26/2023
Drupal core sanitizes filenames with dangerous extensions upon upload (reference: SA-CORE-2020-012) and strips leading and trailing dots from filenames to prevent uploading server configuration files (reference: SA-CORE-2019-010). However, the protections for these two vulnerabilities previously did not work correctly together. As a result, if the site were configured to allow the upload of files with an htaccess extension, these files' filenames would not be properly sanitized. This could allow bypassing the protections provided by Drupal core's default .htaccess files and possible remote code execution on Apache web servers. This issue is mitigated by the fact that it requires a field administrator to explicitly configure a file field to allow htaccess as an extension (a restricted permission), or a contributed module or custom code that overrides allowed file uploads.
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Analysis
by VulDB Data Team • 02/03/2025
The vulnerability described in CVE-2022-25277 represents a critical flaw in Drupal core's file upload sanitization mechanisms that emerged from a failure in the interaction between two previously implemented security measures. This issue specifically affects Drupal core's handling of filename sanitization when files are uploaded through the content management system. The vulnerability stems from the improper coordination between two distinct security protections that were designed to work independently but failed to function correctly in combination. The first protection mechanism strips leading and trailing dots from filenames to prevent the upload of server configuration files, while the second mechanism sanitizes filenames with dangerous extensions to prevent the execution of malicious code. When these protections operate in isolation, they function correctly, but their interaction creates a dangerous gap in the security model.
The technical flaw occurs when a site administrator explicitly configures a file field to permit files with the htaccess extension, which requires restricted permissions typically only available to field administrators. This configuration creates a scenario where the filename sanitization process fails to properly sanitize filenames containing htaccess extensions, despite the system's otherwise robust protections against dangerous file extensions. The vulnerability allows for a bypass of Drupal core's default .htaccess file protections that are specifically designed to prevent remote code execution on Apache web servers. When an attacker uploads a file with an htaccess extension, the system fails to properly sanitize the filename, potentially allowing the uploaded file to be interpreted as an Apache configuration file rather than a regular file.
The operational impact of this vulnerability is significant and potentially severe, as it could enable remote code execution on Apache web servers through carefully crafted file uploads. The attack vector requires a field administrator to explicitly configure the system to allow htaccess extensions, but this configuration represents a critical security misconfiguration that could be exploited by attackers who have gained administrative privileges or through other means of privilege escalation. The vulnerability directly impacts the principle of least privilege and could allow attackers to bypass the layered security controls that Drupal core implements to protect against common web application attacks. This issue aligns with CWE-20, "Improper Input Validation," and CWE-434, "Unrestricted Upload of File with Dangerous Type," demonstrating how the interaction between multiple security controls can create unexpected vulnerabilities.
The mitigation strategies for this vulnerability focus on proper configuration management and access control enforcement. Organizations should ensure that only trusted administrators have the ability to configure file upload settings, particularly those that allow dangerous file extensions. The recommended approach involves maintaining strict control over field administrator permissions and avoiding explicit configuration that permits htaccess extensions unless absolutely necessary. Security teams should implement comprehensive monitoring of file upload activities and maintain strict audit trails of configuration changes. Additionally, the vulnerability highlights the importance of proper security testing and validation of security control interactions, particularly when multiple protection mechanisms are designed to work together. This issue demonstrates the necessity of considering the operational security model and potential attack paths that emerge from the interaction of security controls rather than focusing solely on individual security mechanisms in isolation. The vulnerability also underscores the importance of adhering to the principle of defense in depth, where multiple overlapping security controls work together to provide comprehensive protection against various attack vectors. Organizations should also consider implementing additional security measures such as web application firewalls and file content analysis to provide additional layers of protection beyond the core Drupal security mechanisms.