CWE-1021 Base Incomplete

Improper Restriction of Rendered UI Layers or Frames

This vulnerability occurs when a web application fails to properly control whether its pages can be embedded within frames or UI layers from other websites, potentially misleading users about which…

Definition

What is CWE-1021?

Modern web applications should actively define which external sites, if any, are permitted to display their content within frames, iframes, or similar embedding elements. Without these security headers (like X-Frame-Options or Content-Security-Policy frame-ancestors), your site becomes vulnerable to clickjacking or UI redressing attacks. This allows malicious actors to overlay their own interface on top of yours, tricking users into performing actions unintentionally. To prevent this, developers must implement server-side restrictions that explicitly deny or whitelist permissible domains for embedding. This is a critical client-side security control that protects user interactions and data integrity by ensuring your application's interface is only rendered in a trusted context, preventing confusion and unauthorized actions.

Auswirkungen in der Praxis

Real-world CVEs caused by CWE-1021

CVE-2017-7440

E-mail preview feature in a desktop application allows clickjacking attacks via a crafted e-mail message
CVE-2017-5697

Hardware/firmware product has insufficient clickjacking protection in its web user interface
CVE-2017-4015

Clickjacking in data-loss prevention product via HTTP response header.
CVE-2016-2496

Tapjacking in permission dialog for mobile OS allows access of private storage using a partially-overlapping window.
CVE-2015-1241

Tapjacking in web browser related to page navigation and touch/gesture events.
CVE-2017-0492

System UI in mobile OS allows a malicious application to create a UI overlay of the entire screen to gain privileges.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

1
Identifiziere einen Codepfad, der nicht vertrauenswürdige Eingaben ohne Validierung verarbeitet.
2
Erzeuge eine Payload, die das unsichere Verhalten auslöst — Injection, Traversal, Overflow oder Logik-Missbrauch.
3
Liefere die Payload über einen normalen Request aus und beobachte die Reaktion der Anwendung.
4
Iteriere, bis die Antwort Daten preisgibt, Angreifer-Code ausführt oder Berechtigungen eskaliert.

Verwundbares Codebeispiel

Vulnerable pseudo

MITRE hat kein Codebeispiel für diese CWE veröffentlicht. Das untenstehende Muster ist illustrativ — kanonische Referenzen findest du unter Ressourcen.

Verwundbar pseudo

// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
  // Untrusted input flows directly into the sensitive sink.
  return executeUnsafe(input);
}

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-1021

Implementation The use of X-Frame-Options allows developers of web content to restrict the usage of their application within the form of overlays, frames, or iFrames. The developer can indicate from which domains can frame the content. The concept of X-Frame-Options is well documented, but implementation of this protection mechanism is in development to cover gaps. There is a need for allowing frames from multiple domains.
Implementation A developer can use a "frame-breaker" script in each page that should not be framed. This is very helpful for legacy browsers that do not support X-Frame-Options security feature previously mentioned. It is also important to note that this tactic has been circumvented or bypassed. Improper usage of frames can persist in the web application through nested frames. The "frame-breaking" script does not intuitively account for multiple nested frames that can be presented to the user.
Implementation This defense-in-depth technique can be used to prevent the improper usage of frames in web applications. It prioritizes the valid sources of data to be loaded into the application through the usage of declarative policies. Based on which implementation of Content Security Policy is in use, the developer should use the "frame-ancestors" directive or the "frame-src" directive to mitigate this weakness. Both directives allow for the placement of restrictions when it comes to allowing embedded content.

Erkennungssignale

How to detect CWE-1021

Automated Static Analysis High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Plexicus Auto-Fix

Plexicus erkennt CWE-1021 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-1021?

Wie gravierend ist CWE-1021?

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-1021 betroffen?

MITRE lists the following affected platforms: Web Based.

Wie kann ich CWE-1021 verhindern?

The use of X-Frame-Options allows developers of web content to restrict the usage of their application within the form of overlays, frames, or iFrames. The developer can indicate from which domains can frame the content. The concept of X-Frame-Options is well documented, but implementation of this protection mechanism is in development to cover gaps. There is a need for allowing frames from multiple domains. A developer can use a "frame-breaker" script in each page that should not be framed.…

Wie erkennt und behebt Plexicus CWE-1021?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-1021 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-1021?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/1021.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-1021

CWE-441 Parent

Unintended Proxy or Intermediary ('Confused Deputy')

A confused deputy vulnerability occurs when a system receives a request from a client and forwards it to an external destination without…

CWE-918 Sibling

Server-Side Request Forgery (SSRF)

Server-Side Request Forgery (SSRF) occurs when a web application fetches a remote resource based on user-controlled input, but fails to…

Ressourcen

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