CWE-616 Variant Incomplete

Incomplete Identification of Uploaded File Variables (PHP)

Definition

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the automatic creation of these global variables ('register_globals' is off by default), making this a legacy issue for outdated codebases.

Auswirkungen in der Praxis

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.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

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.

Verwundbares Codebeispiel

Vulnerable PHP

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

Verwundbar 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

Sicheres Codebeispiel

Secure pseudo

Sicher 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.

Präventions-Checkliste

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.

Erkennungssignale

How to detect CWE-616

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-616 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen

Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-616?

Wie gravierend ist CWE-616?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-616 betroffen?

MITRE lists the following affected platforms: PHP.

Wie kann ich CWE-616 verhindern?

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']))

Wie erkennt und behebt Plexicus CWE-616?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-616 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-616?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/616.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-616

CWE-345 Parent

Insufficient Verification of Data Authenticity

This vulnerability occurs when an application fails to properly check where data comes from or confirm its legitimacy, allowing untrusted…

CWE-1293 Sibling

Missing Source Correlation of Multiple Independent Data

This vulnerability occurs when a system trusts a single source of data without verification, making it impossible to detect if that source…

CWE-346 Sibling

Origin Validation Error

This vulnerability occurs when an application fails to properly confirm the true origin of incoming data or communication, allowing…

CWE-347 Sibling

Improper Verification of Cryptographic Signature

This vulnerability occurs when an application fails to properly check the digital signature on data, or skips the verification step…

CWE-348 Sibling

Use of Less Trusted Source

This vulnerability occurs when a system has access to multiple sources for the same critical data, but it chooses to rely on the less…

CWE-349 Sibling

Acceptance of Extraneous Untrusted Data With Trusted Data

This vulnerability occurs when a system processes both trusted and untrusted data together, but fails to separate them. The application…

CWE-351 Sibling

Insufficient Type Distinction

This vulnerability occurs when an application fails to properly differentiate between different types of data or objects, leading to…

CWE-352 Sibling

Cross-Site Request Forgery (CSRF)

Cross-Site Request Forgery (CSRF) happens when a web application cannot reliably tell if a user actually intended to submit a request,…

CWE-353 Sibling

Missing Support for Integrity Check

This vulnerability occurs when a system uses a communication protocol that lacks built-in integrity verification, such as a checksum or…

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