CWE-697 Pilar Incompleto

Incorrect Comparison

This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can create a gap that attackers exploit to bypass checks or…

Definição

What is CWE-697?

This weakness occurs when a security-critical decision relies on a flawed comparison between two pieces of data. The incorrect logic can create a gap that attackers exploit to bypass checks or trigger unintended behavior.

Incorrect comparisons often happen because the check is too simplistic for the security context. For example, a developer might validate only one attribute when multiple factors should be considered, compare the wrong values entirely, or implement the comparison logic incorrectly (like using the wrong operator). This creates a mismatch between the intended security rule and what the code actually enforces. From a developer's perspective, this flaw is a logic bug in a security gate. It's not about missing a check, but about writing a check that doesn't work as intended. To prevent it, carefully review any comparison used for authentication, authorization, input validation, or state change decisions. Ensure it evaluates all necessary conditions with precise logic and test it with both valid and malicious edge cases.

Impacto no mundo real

Real-world CVEs caused by CWE-697

CVE-2021-3116

Chain: Python-based HTTP Proxy server uses the wrong boolean operators (CWE-480) causing an incorrect comparison (CWE-697) that identifies an authN failure if all three conditions are met instead of only one, allowing bypass of the proxy authentication (CWE-1390)
CVE-2020-15811

Chain: Proxy uses a substring search instead of parsing the Transfer-Encoding header (CWE-697), allowing request splitting (CWE-113) and cache poisoning
CVE-2016-10003

Proxy performs incorrect comparison of request headers, leading to infoleak

Como os atacantes a exploram

Trajeto do atacante passo a passo

1
Consider an application in which Truck objects are defined to be the same if they have the same make, the same model, and were manufactured in the same year.
2
Here, the equals() method only checks the make and model of the Truck objects, but the year of manufacture is not included.
3
This example defines a fixed username and password. The AuthenticateUser() function is intended to accept a username and a password from an untrusted user, and check to ensure that it matches the username and password. If the username and password match, AuthenticateUser() is intended to indicate that authentication succeeded.
4
In AuthenticateUser(), the strncmp() call uses the string length of an attacker-provided inPass parameter in order to determine how many characters to check in the password. So, if the attacker only provides a password of length 1, the check will only examine the first byte of the application's password before determining success.
5
As a result, this partial comparison leads to improper authentication (CWE-287).

Exemplo de código vulnerável

Vulnerable Java

Consider an application in which Truck objects are defined to be the same if they have the same make, the same model, and were manufactured in the same year.

Vulnerável Java

public class Truck {
  		private String make;
  		private String model;
  		private int year;
  		public boolean equals(Object o) {
  				if (o == null) return false;
  				if (o == this) return true;
  				if (!(o instanceof Truck)) return false;
  				Truck t = (Truck) o;
  				return (this.make.equals(t.getMake()) && this.model.equals(t.getModel()));
  		}
  }

Payload do atacante

Any of these passwords would still cause authentication to succeed for the "admin" user:

Payload do atacante

p
  pa
  pas
  pass

Exemplo 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 verificação de prevenção

How to prevent CWE-697

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-697

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.

CWE-697

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Perguntas frequentes

Frequently asked questions

O que é o CWE-697?

Qual a gravidade do CWE-697?

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-697?

MITRE lists the following affected platforms: Not Technology-Specific.

Como posso prevenir o CWE-697?

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-697?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-697 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-697?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/697.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-697

CWE-1023 Filho

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Incorrect Comparison

What is CWE-697?

Real-world CVEs caused by CWE-697

Trajeto do atacante passo a passo

Vulnerable Java

Secure pseudo

How to prevent CWE-697

How to detect CWE-697

Don't catalog this weakness. Prove it's reachable.

Frequently asked questions

Weaknesses related to CWE-697

Incomplete Comparison with Missing Factors

Comparison of Incompatible Types

Comparison Using Wrong Factors

Inadequate Detection or Handling of Adversarial Input Perturbations in Automated Recognition Mechanism

Floating Point Comparison with Incorrect Operator

Incorrect Comparison Logic Granularity

Permissive List of Allowed Inputs

Incorrect Regular Expression

Object Model Violation: Just One of Equals and Hashcode Defined

Further reading

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Sample evidence handover

Server-Side Request Forgery in `webhooks/receiver`