CWE-401 Variante Borrador Medium likelihood

Missing Release of Memory after Effective Lifetime

This vulnerability occurs when a program allocates memory but fails to properly release it after it's no longer needed, causing a gradual accumulation of unused memory that can't be reclaimed by the…

Definición

What is CWE-401?

This vulnerability occurs when a program allocates memory but fails to properly release it after it's no longer needed, causing a gradual accumulation of unused memory that can't be reclaimed by the system.
Memory leaks happen when developers allocate memory (e.g., using `malloc()`, `new`, or similar functions) but neglect to free or delete it once the relevant operation is complete. This often stems from complex control flows, error conditions, or long-running processes where tracking every allocation becomes difficult. Over time, especially in servers or persistent applications, these unreleased blocks accumulate, steadily draining available system memory. This resource exhaustion can lead to severe performance degradation, application instability, or complete crashes when the system runs out of memory. To prevent this, developers must ensure that every allocation has a corresponding, guaranteed release, using techniques like automatic resource management (e.g., smart pointers in C++, try-with-resources in Java), rigorous code reviews, and specialized leak detection tools during testing.
Vulnerability Diagram CWE-401
Memory Leak allocate() p = malloc(N) use(p) no free(p) return early repeat ×N heap usage time
Impacto en el mundo real

Real-world CVEs caused by CWE-401

  • CVE-2005-3119

    Memory leak because function does not free() an element of a data structure.

  • CVE-2004-0427

    Memory leak when counter variable is not decremented.

  • CVE-2002-0574

    chain: reference count is not decremented, leading to memory leak in OS by sending ICMP packets.

  • CVE-2005-3181

    Kernel uses wrong function to release a data structure, preventing data from being properly tracked by other code.

  • CVE-2004-0222

    Memory leak via unknown manipulations as part of protocol test suite.

  • CVE-2001-0136

    Memory leak via a series of the same command.

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 C function leaks a block of allocated memory if the call to read() does not return the expected number of bytes:

Vulnerable C 
char* getBlock(int fd) {
  		char* buf = (char*) malloc(BLOCK_SIZE);
  		if (!buf) {
  			return NULL;
  		}
  		if (read(fd, buf, BLOCK_SIZE) != BLOCK_SIZE) {
  				return NULL;
  		}
  		return buf;
  }
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-401

  • Implementation Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone. For example, glibc in Linux provides protection against free of invalid pointers. When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391]. To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.
  • Architecture and Design Use an abstraction library to abstract away risky APIs. Not a complete solution.
  • Architecture and Design / Build and Compilation The Boehm-Demers-Weiser Garbage Collector or valgrind can be used to detect leaks in code.
Señales de detección

How to detect CWE-401

Fuzzing High

Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs - either randomly or algorithmically - and dynamically invoking the code with those inputs. Even with random inputs, it is often capable of generating unexpected results such as crashes, memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases that clearly indicate bugs, which helps developers to diagnose the issues.

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-401 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-401?

This vulnerability occurs when a program allocates memory but fails to properly release it after it's no longer needed, causing a gradual accumulation of unused memory that can't be reclaimed by the system.

¿Qué gravedad tiene CWE-401?

MITRE califica la probabilidad de explotación como Media — la explotación es realista pero suele requerir condiciones específicas.

¿Qué lenguajes o plataformas se ven afectados por CWE-401?

MITRE lists the following affected platforms: C, C++.

¿Cómo puedo prevenir CWE-401?

Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone. For example, glibc in Linux provides protection against free of invalid pointers. When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391]. To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and…

¿Cómo detecta y corrige Plexicus CWE-401?

El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-401 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-401?

MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/401.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.

Debilidades relacionadas

Weaknesses related to CWE-401

CWE-772 Padre

Missing Release of Resource after Effective Lifetime

This vulnerability occurs when a program fails to properly release a system resource—like memory, file handles, or network sockets—after…

CWE-1091 Hermano

Use of Object without Invoking Destructor Method

This weakness occurs when a program accesses an object but fails to properly call its destructor or finalizer method. This leaves the…

CWE-775 Hermano

Missing Release of File Descriptor or Handle after Effective Lifetime

This vulnerability occurs when a program fails to properly close file descriptors or handles after they are no longer needed, leaving…

Recursos

Further reading

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