Pierluigi Paganini
August 02, 2021
Researchers from Wordfence team discovered a vulnerability, tracked as CVE-2021-34639, affecting the WordPress Download Manager plugin that could allow attackers to execute arbitrary code under specific configurations.
The flaw could allow authors and other users with the upload_files capability to upload files with php4 extensions as well as other potentially executable files.
“Prior to our findings, the WordPress Download Manager plugin patched a vulnerability allowing authors and other users with the upload_files capability to upload files with php4 extensions as well as other potentially executable files. While the patch in question was sufficient to protect many configurations, it only checked the very last file extension, so it was still possible to perform a “double extension” attack by uploading a file with multiple extensions.” reads the analysis published by Wordfence. “For instance, it was possible to upload a file titled info.php.png. This file would be executable on certain Apache/mod_php configurations that use an AddHandler or AddType directive.”
The plugin was vulnerable to a double extension attack, that could occur when attackers submit a file with multiple extensions in order to get it being executed.
Experts pointed out that although the CVSS score of this vulnerability is 7.5 (High), its exploitation is not simple because in a real attack scenario the use of an .htaccess file in the downloads directory making it difficult to execute uploaded files.
The flaw impacts versions of WordPress Download Manager prior to 3.1.24. The development team behind the plugin addressed the vulnerability in May.
The development team also addressed a directory traversal issue, tracked as CVE-2021-34638 (CVSS score of 6.5) that could allow a low privileged user (i.e. a contributor) to retrieve the contents of a site’s wp-config.php file by adding a new download and carrying out a directory traversal attack using the file[page_template] parameter.
The flaw could allow an attacker to take over a website either via obtaining database credentials or by executing malicious JavaScript in an administrator’s browser session.
“Since the contents of the file provided in the file[page_template] parameter were echoed out onto the page source, a user with author-level permissions could also upload a file with an image extension containing malicious JavaScript and set the contents of file[page_template] to the path of the uploaded file. This would lead to the JavaScript in the file being executed whenever the page was viewed or previewed resulting in Stored Cross-Site Scripting.” continues the report “As such, and despite the CVSS score of this vulnerability only being a 6.5, it could be used to take over a site either via obtaining database credentials or by executing JavaScript in an administrator’s browser session.”
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