CWE-377 Clase Incompleto

Insecure Temporary File

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.

Definición

What is CWE-377?

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.
Insecure temporary files are a common but dangerous flaw. They happen when developers use predictable filenames, place files in world-writable directories, or set overly permissive file access rights. Attackers can exploit this by 'symlinking' a predictable filename to a critical system file, performing a race condition to replace the file after creation, or simply reading the exposed data. This can lead to information disclosure, data corruption, or even a full system compromise. Preventing this requires using secure, random filenames, setting restrictive file permissions (like 0600), and leveraging secure system APIs designed for temporary file creation. Managing this at scale across numerous applications is difficult; an ASPM like Plexicus can help you track and remediate these flaws across your entire stack. While SAST tools catch the pattern, Plexicus uses AI to suggest the actual code fix, such as replacing insecure `tmpnam()` calls with secure `mkstemp()`, saving hours of manual work.
Impacto en el mundo real

Real-world CVEs caused by CWE-377

  • CVE-2022-41954

    A library uses the Java File.createTempFile() method which creates a file with "-rw-r--r--" default permissions on Unix-like operating systems

Cómo lo explotan los atacantes

Ruta del atacante paso a paso

  1. 1

    Identifica una ruta de código que maneje entrada no confiable sin validación.

  2. 2

    Crea un payload que ejercite el comportamiento inseguro — inyección, traversal, overflow o abuso de lógica.

  3. 3

    Envía el payload a través de una solicitud normal y observa la reacción de la aplicación.

  4. 4

    Itera hasta que la respuesta filtre datos, ejecute código del atacante o escale privilegios.

Ejemplo de código vulnerable

Vulnerable C

The following code uses a temporary file for storing intermediate data gathered from the network before it is processed.

Vulnerable C 
if (tmpnam_r(filename)) {
  		FILE* tmp = fopen(filename,"wb+");
  		while((recv(sock,recvbuf,DATA_SIZE, 0) > 0)&(amt!=0)) amt = fwrite(recvbuf,1,DATA_SIZE,tmp);
  }
  ...
Ejemplo de código seguro

Secure pseudo

Seguro 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-377

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Señales de detección

How to detect CWE-377

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.)

Auto-corrección de Plexicus

Plexicus detecta automáticamente CWE-377 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.

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Preguntas frecuentes

Frequently asked questions

¿Qué es CWE-377?

This vulnerability occurs when an application creates temporary files with insecure permissions or in predictable locations, allowing attackers to read, modify, or delete sensitive data.

¿Qué gravedad tiene CWE-377?

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-377?

MITRE no ha especificado plataformas afectadas para esta CWE — puede aplicar a la mayoría de los stacks de aplicaciones.

¿Cómo puedo prevenir CWE-377?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

¿Cómo detecta y corrige Plexicus CWE-377?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-377 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-377?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/377.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

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Recursos

Further reading

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