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Status: Incomplete Weakness ID: 616 (Weakness Variant)Description Summary The PHP application uses an old method for processing uploaded files by referencing the four global variables that are set for each file (e.g. $varname, $varname_size, $varname_name, $varname_type). These variables could be overwritten by attackers, causing the application to process unauthorized files. Extended Description These global variables could be overwritten by POST requests, cookies, or other methods of populating or overwriting these variables This could be used to read or process arbitrary files by providing values such as "/etc/passwd". Weakness Ordinalities Primary (where the weakness exists independent of other weaknesses) Potential Mitigations Architecture and Design Use PHP 4 or later. Architecture and Design If you must support older PHP versions, write your own version of is_uploaded_file() and run it against $HTTP_POST_FILES['userfile'])) For later PHP versions, reference uploaded files using the $HTTP_POST_FILES or $_FILES variables, and use is_uploaded_file() or move_uploaded_file() to ensure that you are dealing with an uploaded file. Demonstrative Examples Example 1: As of 2006, the "four globals" method is probably in sharp decline, but older PHP applications could have this issue. In the "four globals" method, PHP sets the following 4 global variables (where "varname" is application-dependent): PHP Example: $varname = name of the temporary file on local machine $varname_size = size of file $varname_name = original name of file provided by client $varname_type = MIME type of the file
Example 2: "The global $_FILES exists as of PHP 4.1.0 (Use $HTTP_POST_FILES instead if using an earlier version). These arrays will contain all the uploaded file information." PHP Example: $_FILES['userfile']['name'] - original filename from client $_FILES['userfile']['tmp_name'] - the temp filename of the file on
the server
** note: 'userfile' is the field name from the web form; this can vary. Observed Examples
Other Notes References Shaun Clowes. "A Study in Scarlet - section 5, "File Upload"". Relationships
Taxonomy Mappings
Applicable Platforms Languages PHP Time of Introduction  ImplementationContent History Submissions PLOVER. (Externally Mined) Modifications Eric Dalci. Cigital. 2008-07-01. (External) updated Time_of_Introduction CWE Content Team. MITRE. 2008-09-08. (Internal) updated Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities CWE Content Team. MITRE. 2008-10-14. (Internal) updated Description, Other_Notes, Potential_Mitigations |
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