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 Estável
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…
Definição
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 no 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
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 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.
Exemplo de código vulnerável
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);
} Exemplo 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 verificação de prevenção
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.
Sinais de deteção
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.)
O Plexicus deteta automaticamente o CWE-416 e abre um PR de correção em menos de 60 segundos.
O Codex Remedium analisa cada commit, identifica esta fraqueza exata e entrega um pull request pronto para revisão com o patch. Sem tickets. Sem transferências.
Perguntas frequentes O que é o CWE-416?
Qual a gravidade do CWE-416?
Que linguagens ou plataformas são afetadas pelo CWE-416?
Como posso prevenir o CWE-416?
Como é que o Plexicus deteta e corrige o CWE-416?
Onde posso saber mais sobre o CWE-416?
Frequently asked questions
O que é o 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.
Qual a gravidade do CWE-416?
A MITRE classifica a probabilidade de exploração como Alta — esta fraqueza é ativamente explorada em campo e deve ser priorizada para remediação.
Que linguagens ou plataformas são afetadas pelo CWE-416?
MITRE lists the following affected platforms: C, C++.
Como posso prevenir o 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.
Como é que o Plexicus deteta e corrige o CWE-416?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-416 em cada commit. Quando é encontrada uma correspondência, o nosso agente Codex Remedium abre um PR de correção com o código corrigido, testes e um resumo de uma linha para o revisor.
Onde posso saber mais sobre o CWE-416?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/416.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-416
CWE-825 Pai
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 Irmão
Double Free
A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.
CWE-120 Pode 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 Pode 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
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