MediaWiki 1.22.x before 1.22.2, 1.21.x before 1.21.5, and 1.19.x before 1.19.11, when DjVu or PDF file upload support is enabled, allows remote attackers to execute arbitrary commands via shell metacharacters in (1) the page parameter to includes/media/DjVu.php; (2) the w parameter (aka width field) to thumb.php, which is not properly handled by includes/media/PdfHandler_body.php; and possibly unspecified vectors in (3) includes/media/Bitmap.php and (4) includes/media/ImageHandler.php.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.