CWE-407 Classe Incompleto Low likelihood

Inefficient Algorithmic Complexity

This vulnerability occurs when a software component uses an algorithm with poor worst-case performance. An attacker can exploit this by providing specially crafted input that forces the algorithm…

Definição

What is CWE-407?

This vulnerability occurs when a software component uses an algorithm with poor worst-case performance. An attacker can exploit this by providing specially crafted input that forces the algorithm into its slowest possible execution path, leading to severe performance degradation or denial of service.
At its core, this issue is about predictable resource exhaustion. Common examples include using algorithms with quadratic (O(n²)) or exponential complexity for tasks that handle user-controlled data size, like inefficient sorting or search algorithms on large, attacker-supplied inputs. When exploited, this can cause excessive CPU consumption, memory usage, or runtime delays, crippling the application's availability. Developers can mitigate this by selecting algorithms with consistent, efficient complexity (like O(n log n) for sorting) and implementing safeguards. These include setting hard limits on input size, using timeouts for operations, and switching to more performant algorithms or data structures when processing thresholds are crossed. Always profile code with worst-case input scenarios during testing.
Impacto no mundo real

Real-world CVEs caused by CWE-407

  • CVE-2021-32617

    C++ library for image metadata has "quadratic complexity" issue with unnecessarily repetitive parsing each time an invalid character is encountered

  • CVE-2020-10735

    Python has "quadratic complexity" issue when converting string to int with many digits in unexpected bases

  • CVE-2020-5243

    server allows ReDOS with crafted User-Agent strings, due to overlapping capture groups that cause excessive backtracking.

  • CVE-2014-1474

    Perl-based email address parser has "quadratic complexity" issue via a string that does not contain a valid address

  • CVE-2003-0244

    CPU consumption via inputs that cause many hash table collisions.

  • CVE-2003-0364

    CPU consumption via inputs that cause many hash table collisions.

  • CVE-2002-1203

    Product performs unnecessary processing before dropping an invalid packet.

  • CVE-2001-1501

    CPU and memory consumption using many wildcards.

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    This example attempts to check if an input string is a "sentence" [REF-1164].

  2. 2

    The regular expression has a vulnerable backtracking clause inside (\w+\s?)*$ which can be triggered to cause a Denial of Service by processing particular phrases. To fix the backtracking problem, backtracking is removed with the ?= portion of the expression which changes it to a lookahead and the \2 which prevents the backtracking. The modified example is:

  3. 3

    Note that [REF-1164] has a more thorough (and lengthy) explanation of everything going on within the RegEx.

Exemplo de código vulnerável

Vulnerable JavaScript

This example attempts to check if an input string is a "sentence" [REF-1164].

Vulnerável JavaScript 
var test_string = "Bad characters: $@#";
 var bad_pattern = /^(\w+\s?)*$/i;
 var result = test_string.search(bad_pattern);
Exemplo de código seguro

Secure JavaScript

The regular expression has a vulnerable backtracking clause inside (\w+\s?)*$ which can be triggered to cause a Denial of Service by processing particular phrases. To fix the backtracking problem, backtracking is removed with the ?= portion of the expression which changes it to a lookahead and the \2 which prevents the backtracking. The modified example is:

Seguro JavaScript 
var test_string = "Bad characters: $@#";
 var good_pattern = /^((?=(\w+))\2\s?)*$/i;
 var result = test_string.search(good_pattern);
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-407

  • 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-407

SAST High

Executar análise estática (SAST) na base de código à procura do padrão inseguro no fluxo de dados.

DAST Moderate

Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.

Runtime Moderate

Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.

Code review Moderate

Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-407 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-407?

This vulnerability occurs when a software component uses an algorithm with poor worst-case performance. An attacker can exploit this by providing specially crafted input that forces the algorithm into its slowest possible execution path, leading to severe performance degradation or denial of service.

Qual a gravidade do CWE-407?

A MITRE classifica a probabilidade de exploração como Baixa — a exploração é pouco comum, mas a fraqueza deve mesmo assim ser corrigida quando descoberta.

Que linguagens ou plataformas são afetadas pelo CWE-407?

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

Como posso prevenir o CWE-407?

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-407?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-407 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-407?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/407.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-407

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CWE-1072 Irmão

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CWE-1073 Irmão

Non-SQL Invokable Control Element with Excessive Number of Data Resource Accesses

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CWE-1084 Irmão

Invokable Control Element with Excessive File or Data Access Operations

This weakness occurs when a single function or method performs an excessive number of file or database operations, such as repeated reads,…

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Large Data Table with Excessive Number of Indices

This weakness occurs when an application uses a database table with a very large number of rows and creates too many indexes on it,…

CWE-1094 Irmão

Excessive Index Range Scan for a Data Resource

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CWE-1176 Irmão

Inefficient CPU Computation

This weakness occurs when software uses inefficient algorithms or suboptimal CPU operations, performing unnecessary or overly complex…

CWE-406 Irmão

Insufficient Control of Network Message Volume (Network Amplification)

This vulnerability occurs when a system fails to properly limit the amount of network traffic it can generate in response to a request,…

Recursos

Further reading

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