Updates released on Wednesday for the Drupal content management system (CMS) patch a remote code execution vulnerability related to failure to properly sanitize the names of uploaded files.
The vulnerability, tracked as CVE-2020-13671, has been classified as critical, but it’s worth mentioning that Drupal uses the NIST Common Misuse Scoring System, which assigns vulnerabilities a score ranging between 0 and 25, with “critical” being only the second highest rating, after “highly critical.”
An attacker who can upload files to a server can use certain types of extensions to bypass restrictions and get malicious code executed.
“Drupal core does not properly sanitize certain filenames on uploaded files, which can lead to files being interpreted as the incorrect extension and served as the wrong MIME type or executed as PHP for certain hosting configurations,” Drupal explained in an advisory.
The issue was reported to Drupal developers by several people, and it has been patched in Drupal 7, 8 and 9 with the release of versions 7.74, 8.8.11, 8.9.9 and 9.0.8.
Drupal has also advised users to check their servers for files with potentially malicious extensions, such as filename.php.txt or filename.html.gif. Users should be on the lookout for files that have extensions such as phar, php, pl, py, cgi, html, htm, phtml, js, and asp.
This is the fifth round of security updates released this year by Drupal developers. In March they updated the CKEditor to patch XSS vulnerabilities, in May they addressed XSS and open redirect flaws, in June they fixed code execution and several other types of issues, and in September they patched XSS and information disclosure vulnerabilities.