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CWE-784 Variante Rascunho
Reliance on Cookies without Validation and Integrity Checking in a Security Decision
This vulnerability occurs when an application makes security decisions—like granting access or verifying identity—based solely on cookie data without first confirming the cookie's authenticity or…
Definição
What is CWE-784?
This vulnerability occurs when an application makes security decisions—like granting access or verifying identity—based solely on cookie data without first confirming the cookie's authenticity or integrity.
Attackers can easily manipulate cookie values directly in the browser or by crafting custom client-side requests. Since the application trusts this data without validation, attackers can forge cookies to impersonate other users, bypass login screens, or escalate their privileges by inserting expected values.
To prevent this, developers must never treat cookies as a trusted security mechanism on their own. Always validate and verify cookie integrity on the server using techniques like cryptographic signing, comparing against server-side sessions, or using secure, tamper-proof tokens instead of plain data.
Impacto no mundo real
Real-world CVEs caused by CWE-784
-
Attacker can bypass authentication by setting a cookie to a specific value.
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Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
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Content management system allows admin privileges by setting a "login" cookie to "OK."
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e-dating application allows admin privileges by setting the admin cookie to 1.
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Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
The following code excerpt reads a value from a browser cookie to determine the role of the user.
- 2
The following code could be for a medical records application. It performs authentication by checking if a cookie has been set.
- 3
The programmer expects that the AuthenticateUser() check will always be applied, and the "authenticated" cookie will only be set when authentication succeeds. The programmer even diligently specifies a 2-hour expiration for the cookie.
- 4
However, the attacker can set the "authenticated" cookie to a non-zero value such as 1. As a result, the $auth variable is 1, and the AuthenticateUser() check is not even performed. The attacker has bypassed the authentication.
- 5
In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.
Exemplo de código vulnerável
Vulnerable Java
The following code excerpt reads a value from a browser cookie to determine the role of the user.
Cookie[] cookies = request.getCookies();
for (int i =0; i< cookies.length; i++) {
Cookie c = cookies[i];
if (c.getName().equals("role")) {
userRole = c.getValue();
}
} 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-784
- Architecture and Design Avoid using cookie data for a security-related decision.
- Implementation Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.
- Architecture and Design Add integrity checks to detect tampering.
- Architecture and Design Protect critical cookies from replay attacks, since cross-site scripting or other attacks may allow attackers to steal a strongly-encrypted cookie that also passes integrity checks. This mitigation applies to cookies that should only be valid during a single transaction or session. By enforcing timeouts, you may limit the scope of an attack. As part of your integrity check, use an unpredictable, server-side value that is not exposed to the client.
Sinais de deteção
How to detect CWE-784
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.
CWE-784
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Perguntas frequentes O que é o CWE-784?
Qual a gravidade do CWE-784?
Que linguagens ou plataformas são afetadas pelo CWE-784?
Como posso prevenir o CWE-784?
Como é que o Plexicus deteta e corrige o CWE-784?
Onde posso saber mais sobre o CWE-784?
Frequently asked questions
O que é o CWE-784?
This vulnerability occurs when an application makes security decisions—like granting access or verifying identity—based solely on cookie data without first confirming the cookie's authenticity or integrity.
Qual a gravidade do CWE-784?
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-784?
MITRE lists the following affected platforms: Web Based.
Como posso prevenir o CWE-784?
Avoid using cookie data for a security-related decision. Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision.
Como é que o Plexicus deteta e corrige o CWE-784?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-784 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-784?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/784.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-784
Pronto para validar o que importa?
Pronto para validar o que importa.
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