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.)
CWE-1021 Base Incompleto
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…
Definición
What is CWE-1021?
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 site they are interacting with.
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.
Impacto en el mundo real
Real-world CVEs caused by CWE-1021
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E-mail preview feature in a desktop application allows clickjacking attacks via a crafted e-mail message
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Hardware/firmware product has insufficient clickjacking protection in its web user interface
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Clickjacking in data-loss prevention product via HTTP response header.
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Tapjacking in permission dialog for mobile OS allows access of private storage using a partially-overlapping window.
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Tapjacking in web browser related to page navigation and touch/gesture events.
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System UI in mobile OS allows a malicious application to create a UI overlay of the entire screen to gain privileges.
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
Identifica una ruta de código que maneje entrada no confiable sin validación.
- 2
Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.
- 3
Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.
- 4
Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.
Ejemplo de código vulnerable
Vulnerable pseudo
MITRE no ha publicado un ejemplo de código para esta CWE. El patrón siguiente es ilustrativo — consulta Recursos para referencias canónicas.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} Ejemplo de código seguro
Secure 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.
Lista de prevención
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.
Señales de detección
How to detect CWE-1021
Plexicus detecta automáticamente CWE-1021 y abre un PR de corrección en menos de 60 segundos.
Codex Remedium escanea cada commit, identifica esta debilidad concreta y entrega un pull request listo para revisión con el parche. Sin tickets. Sin traspasos.
Preguntas frecuentes ¿Qué es CWE-1021?
¿Qué gravedad tiene CWE-1021?
¿Qué lenguajes o plataformas se ven afectados por CWE-1021?
¿Cómo puedo prevenir CWE-1021?
¿Cómo detecta y corrige Plexicus CWE-1021?
¿Dónde puedo aprender más sobre CWE-1021?
Frequently asked questions
¿Qué es CWE-1021?
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 site they are interacting with.
¿Qué gravedad tiene CWE-1021?
MITRE no ha publicado una calificación de probabilidad de explotación para esta debilidad. Trátala como de impacto medio hasta que tu modelo de amenazas demuestre lo contrario.
¿Qué lenguajes o plataformas se ven afectados por CWE-1021?
MITRE lists the following affected platforms: Web Based.
¿Cómo puedo prevenir CWE-1021?
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.…
¿Cómo detecta y corrige Plexicus CWE-1021?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-1021 en cada commit. Cuando hay coincidencia, nuestro agente Codex Remedium abre un PR de corrección con el código corregido, las pruebas y un resumen de una línea para el revisor.
¿Dónde puedo aprender más sobre CWE-1021?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/1021.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-1021
CWE-441 Padre
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 Hermano
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…
Recursos
Further reading
- MITRE — CWE-1021 oficial https://cwe.mitre.org/data/definitions/1021.html
- Clickjacking For Shells https://www.exploit-db.com/docs/17881.pdf
- Clickjacking - OWASP https://owasp.org/www-community/attacks/Clickjacking
- SecTheory https://www.sectheory.com/clickjacking.htm
- Content Security Policy Level 3 https://w3c.github.io/webappsec-csp/
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