CWE-616 Variante Incomplet

Incomplete Identification of Uploaded File Variables (PHP)

Définition

What is CWE-616?

This vulnerability occurs in PHP applications that rely on the deprecated, auto-registered global variables for file uploads (like $varname, $varname_size). Because these variables are not properly validated, an attacker can overwrite them to trick the application into processing malicious or unauthorized files.

In older PHP configurations, file uploads automatically created a set of global variables for each file. Attackers can exploit this by sending forged POST requests or manipulated cookies that overwrite these variables with their own values. Since the application trusts these globals without verification, it can be deceived into handling files it was never intended to, such as sensitive system files. To prevent this, developers must stop using these legacy global variables entirely. The secure alternative is to use the validated $_FILES superglobal array, which is populated directly by the PHP engine and is immune to this type of user-supplied data overwrite. Modern PHP versions have disabled the automatic creation of these global variables ('register_globals' is off by default), making this a legacy issue for outdated codebases.

Impact réel

Real-world CVEs caused by CWE-616

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-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-2002-1710

Product does not distinguish uploaded file from other files.

Comment les attaquants l'exploitent

Parcours de l'attaquant étape par étape

1
As of 2006, the "four globals" method is probably in sharp decline, but older PHP applications could have this issue.
2
In the "four globals" method, PHP sets the following 4 global variables (where "varname" is application-dependent):
3
"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."
4
** note: 'userfile' is the field name from the web form; this can vary.

Exemple de code vulnérable

Vulnerable PHP

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

Vulnérable PHP

$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

Exemple de code sécurisé

Secure pseudo

Sécurisé pseudo

// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}

What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.

Liste de contrôle de prévention

How to prevent CWE-616

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']))
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.

Signaux de détection

How to detect CWE-616

SAST High

Exécuter une analyse statique (SAST) sur le code source à la recherche du motif non sécurisé dans le flux de données.

DAST Moderate

Exécuter des tests de sécurité applicative dynamique (DAST) contre le point de terminaison en ligne.

Runtime Moderate

Surveiller les journaux runtime pour détecter des traces d'exception inhabituelles, des entrées malformées ou des tentatives de contournement d'autorisation.

Code review Moderate

Revue de code : signaler tout nouveau code qui traite les entrées de cette surface sans utiliser les helpers du framework validés.

Correction automatique Plexicus

Plexicus détecte automatiquement CWE-616 et ouvre une PR de correction en moins de 60 secondes.

Codex Remedium analyse chaque commit, identifie cette faiblesse précise et livre une pull request prête à être relue avec le correctif. Pas de tickets. Pas de transferts.

Obtenir une démo Essayer Plexicus gratuitement

Questions fréquentes

Frequently asked questions

Qu'est-ce que CWE-616 ?

Quelle est la gravité de CWE-616 ?

MITRE n'a pas publié de note de probabilité d'exploitation pour cette faiblesse. Traitez-la comme un impact moyen jusqu'à ce que votre modèle de menace prouve le contraire.

Quels langages ou plateformes sont affectés par CWE-616 ?

MITRE lists the following affected platforms: PHP.

Comment puis-je prévenir CWE-616 ?

Use PHP 4 or later. If you must support older PHP versions, write your own version of is_uploaded_file() and run it against $HTTP_POST_FILES['userfile']))

Comment Plexicus détecte et corrige CWE-616 ?

Le moteur SAST de Plexicus reconnaît la signature de flux de données de CWE-616 à chaque commit. Lorsqu'une correspondance est trouvée, notre agent Codex Remedium ouvre une PR de correction avec le code corrigé, les tests et un résumé d'une ligne pour le relecteur.

Où puis-je en savoir plus sur CWE-616 ?

MITRE publie la définition canonique à https://cwe.mitre.org/data/definitions/616.html. Vous pouvez également consulter la documentation OWASP et NIST pour des conseils adjacents.

Faiblesses associées

Weaknesses related to CWE-616

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