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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
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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)
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Chain: Proxy uses a substring search instead of parsing the Transfer-Encoding header (CWE-697), allowing request splitting (CWE-113) and cache poisoning
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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.
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:
p
pa
pas
pass 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-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
Executar testes dinâmicos de segurança de aplicações (DAST) contra o endpoint em execução.
Monitorizar os registos em tempo de execução para traços de exceção invulgares, input malformado ou tentativas de contornar a autorização.
Revisão de código: sinalizar qualquer novo código que trate input desta superfície sem usar os ajudantes validados do framework.
O Plexicus deteta automaticamente o CWE-697 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-697?
Qual a gravidade do CWE-697?
Que linguagens ou plataformas são afetadas pelo CWE-697?
Como posso prevenir o CWE-697?
Como é que o Plexicus deteta e corrige o CWE-697?
Onde posso saber mais sobre o CWE-697?
Frequently asked questions
O que é o 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.
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
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