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.
CWE-416 Variante Estable
Use After Free
Use After Free happens when a program continues to use a pointer to a memory location after that memory has been freed. This can lead to unpredictable behavior, crashes, or security vulnerabilities…
Definición
What is CWE-416?
Use After Free happens when a program continues to use a pointer to a memory location after that memory has been freed. This can lead to unpredictable behavior, crashes, or security vulnerabilities because the freed memory may have been reallocated for a different purpose.
This vulnerability occurs because the pointer isn't invalidated after `free()` is called. The memory manager can then reassign that same memory block to a different part of the program, perhaps for storing unrelated data. When the original, now 'dangling' pointer is used again, it reads or writes to this new data, corrupting it and leading to instability or exploitable conditions like arbitrary code execution.
Detecting use-after-free bugs manually is challenging as they often depend on complex, state-specific execution paths. While SAST tools can flag the dangerous pattern, Plexicus uses AI to analyze context and suggest precise code fixes—such as nullifying pointers or reordering logic—saving developers hours of manual debugging and helping secure the entire application lifecycle.
Impacto en el mundo real
Real-world CVEs caused by CWE-416
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Chain: an operating system kernel has insufficent resource locking (CWE-413) leading to a use after free (CWE-416).
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Chain: two threads in a web browser use the same resource (CWE-366), but one of those threads can destroy the resource before the other has completed (CWE-416).
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Chain: mobile platform race condition (CWE-362) leading to use-after-free (CWE-416), as exploited in the wild per CISA KEV.
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Chain: race condition (CWE-362) leads to use-after-free (CWE-416), as exploited in the wild per CISA KEV.
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Use-after-free triggered by closing a connection while data is still being transmitted.
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Improper allocation for invalid data leads to use-after-free.
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certificate with a large number of Subject Alternate Names not properly handled in realloc, leading to use-after-free
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Timers are not disabled when a related object is deleted
Cómo lo explotan los atacantes
Ruta del atacante paso a paso
- 1
The following example demonstrates the weakness.
- 2
The following code illustrates a use after free error:
- 3
When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.
Ejemplo de código vulnerable
Vulnerable C
The following example demonstrates the weakness.
#include <stdio.h>
#include <unistd.h>
#define BUFSIZER1 512
#define BUFSIZER2 ((BUFSIZER1/2) - 8)
int main(int argc, char **argv) {
char *buf1R1;
char *buf2R1;
char *buf2R2;
char *buf3R2;
buf1R1 = (char *) malloc(BUFSIZER1);
buf2R1 = (char *) malloc(BUFSIZER1);
free(buf2R1);
buf2R2 = (char *) malloc(BUFSIZER2);
buf3R2 = (char *) malloc(BUFSIZER2);
strncpy(buf2R1, argv[1], BUFSIZER1-1);
free(buf1R1);
free(buf2R2);
free(buf3R2);
} 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-416
- Architecture and Design Choose a language that provides automatic memory management.
- Implementation When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Señales de detección
How to detect CWE-416
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-416
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Preguntas frecuentes ¿Qué es CWE-416?
¿Qué gravedad tiene CWE-416?
¿Qué lenguajes o plataformas se ven afectados por CWE-416?
¿Cómo puedo prevenir CWE-416?
¿Cómo detecta y corrige Plexicus CWE-416?
¿Dónde puedo aprender más sobre CWE-416?
Frequently asked questions
¿Qué es CWE-416?
Use After Free happens when a program continues to use a pointer to a memory location after that memory has been freed. This can lead to unpredictable behavior, crashes, or security vulnerabilities because the freed memory may have been reallocated for a different purpose.
¿Qué gravedad tiene CWE-416?
MITRE califica la probabilidad de explotación como Alta — esta debilidad se explota activamente en la práctica y debe priorizarse para su remediación.
¿Qué lenguajes o plataformas se ven afectados por CWE-416?
MITRE lists the following affected platforms: C, C++.
¿Cómo puedo prevenir CWE-416?
Choose a language that provides automatic memory management. When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
¿Cómo detecta y corrige Plexicus CWE-416?
El motor SAST de Plexicus detecta la firma de flujo de datos para CWE-416 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-416?
MITRE publica la definición canónica en https://cwe.mitre.org/data/definitions/416.html. También puedes consultar la documentación de OWASP y NIST para guías relacionadas.
Debilidades relacionadas
Weaknesses related to CWE-416
CWE-825 Padre
Expired Pointer Dereference
This vulnerability occurs when a program tries to use a pointer that still points to a memory location that has already been freed or…
CWE-415 Hermano
Double Free
A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.
CWE-120 Puede preceder
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
This vulnerability occurs when a program copies data from one memory location to another without first verifying that the source data will…
CWE-123 Puede preceder
Write-what-where Condition
A write-what-where condition occurs when an attacker can control both the data written and the exact memory location where it's written,…
Recursos
Further reading
- MITRE — CWE-416 oficial https://cwe.mitre.org/data/definitions/416.html
- Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors https://samate.nist.gov/SSATTM_Content/papers/Seven%20Pernicious%20Kingdoms%20-%20Taxonomy%20of%20Sw%20Security%20Errors%20-%20Tsipenyuk%20-%20Chess%20-%20McGraw.pdf
- The CLASP Application Security Process https://cwe.mitre.org/documents/sources/TheCLASPApplicationSecurityProcess.pdf
¿Listo para validar lo que importa?
Listo para validar lo que importa.
Plexicus es Proof-Driven AppSec: hallazgos validados, comprensión contextual y remediación revisada — anclada en evidencia, acotada contigo.