CWE-616: Incomplete Identification of Uploaded File Variables (PHP)

Description

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".

ThreatScore

Threat Mapped score: 0.0

Industry: Finiancial

Threat priority: Unclassified

Observed Examples (CVEs)

CVE: CVE-2002-1460

Forum does not properly verify whether a file was uploaded or if the associated variables were set by POST, allowing remote attackers to read arbitrary files.
CVE: CVE-2002-1759

Product doesn't check if the variables for an upload were set by uploading the file, or other methods such as $_POST.
CVE: CVE-2002-1710

Product does not distinguish uploaded file from other files.

Related Attack Patterns (CAPEC)

N/A

Attack TTPs

N/A

Modes of Introduction

Phase	Note
Implementation	N/A

Common Consequences

Impact: Read Files or Directories, Modify Files or Directories — Notes:

Potential Mitigations

Architecture and Design: Use PHP 4 or later. (N/A)
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'])) (N/A)
Implementation: 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. (N/A)

Applicable Platforms

PHP (N/A, Undetermined)

Demonstrative Examples

Intro: As of 2006, the "four globals" method is probably in sharp decline, but older PHP applications could have this issue.

Body: In the "four globals" method, PHP sets the following 4 global variables (where "varname" is application-dependent):

$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

Intro: "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."

Body: ** note: 'userfile' is the field name from the web form; this can vary.

$_FILES['userfile']['name'] - original filename from client $_FILES['userfile']['tmp_name'] - the temp filename of the file on the server

Notes

No notes available.

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