CWE-834 Classe Incompleto

Excessive Iteration

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.

Definição

What is CWE-834?

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.
When an attacker can control or influence the loop's conditions, they can force it to run far more times than intended. This quickly drains system resources like CPU cycles and memory, potentially causing slowdowns, service denial, or crashes. Even a loop that isn't technically infinite can be dangerous if each pass consumes significant resources. For developers, the core issue is trusting unvalidated input to control loop counters or termination logic. To prevent this, always enforce explicit, reasonable upper bounds on all iterative processes, especially those influenced by external data like user input, file contents, or network responses.
Impacto no mundo real

Real-world CVEs caused by CWE-834

  • CVE-2011-1027

    Chain: off-by-one error (CWE-193) leads to infinite loop (CWE-835) using invalid hex-encoded characters.

  • CVE-2006-6499

    Chain: web browser crashes due to infinite loop - "bad looping logic [that relies on] floating point math [CWE-1339] to exit the loop [CWE-835]"

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    In this example a mistake exists in the code where the exit condition contained in flg is never called. This results in the function calling itself over and over again until the stack is exhausted.

  2. 2

    Note that the only difference between the Good and Bad examples is that the recursion flag will change value and cause the recursive call to return.

  3. 3

    For this example, the method isReorderNeeded is part of a bookstore application that determines if a particular book needs to be reordered based on the current inventory count and the rate at which the book is being sold.

  4. 4

    However, the while loop will become an infinite loop if the rateSold input parameter has a value of zero since the inventoryCount will never fall below the minimumCount. In this case the input parameter should be validated to ensure that a value of zero does not cause an infinite loop, as in the following code.

Exemplo de código vulnerável

Vulnerable C

In this example a mistake exists in the code where the exit condition contained in flg is never called. This results in the function calling itself over and over again until the stack is exhausted.

Vulnerável C 
void do_something_recursive (int flg)
 {

```
   ... // Do some real work here, but the value of flg is unmodified
   if (flg) { do_something_recursive (flg); } // flg is never modified so it is always TRUE - this call will continue until the stack explodes
 }
 int flag = 1; // Set to TRUE
 do_something_recursive (flag);
Exemplo de código seguro

Secure C

Note that the only difference between the Good and Bad examples is that the recursion flag will change value and cause the recursive call to return.

Seguro C 
void do_something_recursive (int flg)
 {

```
   ... // Do some real work here
   // Modify value of flg on done condition
   if (flg) { do_something_recursive (flg); } // returns when flg changes to 0
 }
 int flag = 1; // Set to TRUE
 do_something_recursive (flag);
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-834

  • 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.
Sinais de deteção

How to detect CWE-834

Dynamic Analysis with Manual Results Interpretation SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Fuzz Tester Framework-based Fuzzer Forced Path Execution

Manual Static Analysis - Source Code SOAR Partial

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Cost effective for partial coverage: ``` Focused Manual Spotcheck - Focused manual analysis of source Manual Source Code Review (not inspections)

Automated Static Analysis - Source Code High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Context-configured Source Code Weakness Analyzer

Architecture or Design Review High

According to SOAR [REF-1479], the following detection techniques may be useful: ``` Highly cost effective: ``` Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-834 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.

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Perguntas frequentes

Frequently asked questions

O que é o CWE-834?

This vulnerability occurs when a program runs a loop too many times because it lacks proper limits on its iterations.

Qual a gravidade do CWE-834?

A MITRE não publicou uma classificação de probabilidade de exploração para esta fraqueza. Trate-a como impacto médio até o seu modelo de ameaças provar o contrário.

Que linguagens ou plataformas são afetadas pelo CWE-834?

A MITRE não especificou as plataformas afetadas por este CWE — pode aplicar-se à maioria das stacks de aplicações.

Como posso prevenir o CWE-834?

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.

Como é que o Plexicus deteta e corrige o CWE-834?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-834 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-834?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/834.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

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Recursos

Further reading

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