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CWE-96 Base Rascunho
Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection')
Static Code Injection occurs when an application incorporates unvalidated or improperly sanitized user input directly into a static, executable resource like a configuration file, template, or…
Definição
What is CWE-96?
Static Code Injection occurs when an application incorporates unvalidated or improperly sanitized user input directly into a static, executable resource like a configuration file, template, or library. Because this input is saved and later executed, it allows an attacker to inject malicious code that becomes a permanent part of the application's logic.
This vulnerability is dangerous because the injected code becomes embedded within a file that the system trusts and executes automatically. Unlike attacks that only affect a single transaction, a successful static code injection can persistently compromise the application, leading to ongoing data theft, system takeover, or service disruption every time the compromised resource is used.
To prevent it, developers must treat all data destined for static files as untrusted. Implement strict input validation using allowlists for expected values and context-specific output encoding or sanitization before writing data to configuration files, templates, or scripts. Never construct executable code by simply concatenating user input.
Impacto no mundo real
Real-world CVEs caused by CWE-96
-
Perl code directly injected into CGI library file from parameters to another CGI program.
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Direct PHP code injection into supporting template file.
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Direct code injection into PHP script that can be accessed by attacker.
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PHP code from User-Agent HTTP header directly inserted into log file implemented as PHP script.
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chain: execution after redirect allows non-administrator to perform static code injection.
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
This example attempts to write user messages to a message file and allow users to view them.
- 2
While the programmer intends for the MessageFile to only include data, an attacker can provide a message such as:
- 3
which will decode to the following:
- 4
The programmer thought they were just including the contents of a regular data file, but PHP parsed it and executed the code. Now, this code is executed any time people view messages.
- 5
Notice that XSS (CWE-79) is also possible in this situation.
Exemplo de código vulnerável
Vulnerable PHP
This example attempts to write user messages to a message file and allow users to view them.
$MessageFile = "messages.out";
if ($_GET["action"] == "NewMessage") {
$name = $_GET["name"];
$message = $_GET["message"];
$handle = fopen($MessageFile, "a+");
fwrite($handle, "<b>$name</b> says '$message'<hr>\n");
fclose($handle);
echo "Message Saved!<p>\n";
}
else if ($_GET["action"] == "ViewMessages") {
include($MessageFile);
} Payload do atacante
While the programmer intends for the MessageFile to only include data, an attacker can provide a message such as:
name=h4x0r
message=%3C?php%20system(%22/bin/ls%20-l%22);?%3E 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-96
- Implementation Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Implementation Perform proper output validation and escaping to neutralize all code syntax from data written to code files.
Sinais de deteção
How to detect CWE-96
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-96
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Perguntas frequentes O que é o CWE-96?
Qual a gravidade do CWE-96?
Que linguagens ou plataformas são afetadas pelo CWE-96?
Como posso prevenir o CWE-96?
Como é que o Plexicus deteta e corrige o CWE-96?
Onde posso saber mais sobre o CWE-96?
Frequently asked questions
O que é o CWE-96?
Static Code Injection occurs when an application incorporates unvalidated or improperly sanitized user input directly into a static, executable resource like a configuration file, template, or library. Because this input is saved and later executed, it allows an attacker to inject malicious code that becomes a permanent part of the application's logic.
Qual a gravidade do CWE-96?
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-96?
MITRE lists the following affected platforms: PHP, Perl, Interpreted.
Como posso prevenir o CWE-96?
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and…
Como é que o Plexicus deteta e corrige o CWE-96?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-96 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-96?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/96.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
Weaknesses related to CWE-96
CWE-94 Pai
Improper Control of Generation of Code ('Code Injection')
This vulnerability occurs when an application builds executable code using unvalidated external input, such as user data. Because the…
CWE-1336 Irmão
Improper Neutralization of Special Elements Used in a Template Engine
This vulnerability occurs when an application uses a template engine to process user-controlled input but fails to properly sanitize…
CWE-95 Irmão
Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
This vulnerability occurs when an application takes user input and passes it directly into a dynamic code execution function, like eval(),…
CWE-97 Filho
Improper Neutralization of Server-Side Includes (SSI) Within a Web Page
This vulnerability occurs when a web application dynamically generates pages but fails to properly sanitize user-supplied input that could…
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