Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
CWE-567 Base Rascunho
Unsynchronized Access to Shared Data in a Multithreaded Context
This vulnerability occurs when multiple threads in an application can read and modify shared data, like static variables, without proper coordination. This unsynchronized access corrupts data,…
Definição
What is CWE-567?
This vulnerability occurs when multiple threads in an application can read and modify shared data, like static variables, without proper coordination. This unsynchronized access corrupts data, causes crashes, and leads to unpredictable, often security-critical, behavior.
A common example is in Java servlet-based applications, where the framework manages multithreading. Developers might mistakenly treat static variables as safe, forgetting that all servlet threads can access them simultaneously. If an attacker can influence this shared data, one thread could inject invalid or malicious content that another thread then processes, creating a serious security flaw.
This issue is not limited to servlets or J2EE. It's a fundamental concurrency flaw that can appear in any multithreaded environment when developers assume single-threaded execution for shared resources. The core problem is a mismatch: the application uses a multithreaded architecture but fails to implement the necessary safeguards, like locks or atomic operations, to protect its shared state from concurrent modification.
Impacto no mundo real
Real-world CVEs caused by CWE-567
Ainda não há referências CVE públicas associadas a este CWE no catálogo da MITRE.
Como os atacantes a exploram
Trajeto do atacante passo a passo
- 1
The following code implements a basic counter for how many times the page has been accesed.
- 2
Consider when two separate threads, Thread A and Thread B, concurrently handle two different requests:
- 3
- Assume this is the first occurrence of doGet, so the value of count is 0. - doGet() is called within Thread A. - The execution of doGet() in Thread A continues to the point AFTER the value of the count variable is read, then incremented, but BEFORE it is saved back to count. At this stage, the incremented value is 1, but the value of count is 0. - doGet() is called within Thread B, and due to a higher thread priority, Thread B progresses to the point where the count variable is accessed (where it is still 0), incremented, and saved. After the save, count is 1. - Thread A continues. It saves the intermediate, incremented value to the count variable - but the incremented value is 1, so count is "re-saved" to 1.
- 4
At this point, both Thread A and Thread B print that one hit has been seen, even though two separate requests have been processed. The value of count should be 2, not 1.
- 5
While this example does not have any real serious implications, if the shared variable in question is used for resource tracking, then resource consumption could occur. Other scenarios exist.
Exemplo de código vulnerável
Vulnerable Java
The following code implements a basic counter for how many times the page has been accesed.
public static class Counter extends HttpServlet {
static int count = 0;
protected void doGet(HttpServletRequest in, HttpServletResponse out)
throws ServletException, IOException {
out.setContentType("text/plain");
PrintWriter p = out.getWriter();
count++;
p.println(count + " hits so far!");
}
} 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-567
- Implementation Remove the use of static variables used between servlets. If this cannot be avoided, use synchronized access for these variables.
Sinais de deteção
How to detect CWE-567
O Plexicus deteta automaticamente o CWE-567 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-567?
Qual a gravidade do CWE-567?
Que linguagens ou plataformas são afetadas pelo CWE-567?
Como posso prevenir o CWE-567?
Como é que o Plexicus deteta e corrige o CWE-567?
Onde posso saber mais sobre o CWE-567?
Frequently asked questions
O que é o CWE-567?
This vulnerability occurs when multiple threads in an application can read and modify shared data, like static variables, without proper coordination. This unsynchronized access corrupts data, causes crashes, and leads to unpredictable, often security-critical, behavior.
Qual a gravidade do CWE-567?
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-567?
MITRE lists the following affected platforms: Java.
Como posso prevenir o CWE-567?
Remove the use of static variables used between servlets. If this cannot be avoided, use synchronized access for these variables.
Como é que o Plexicus deteta e corrige o CWE-567?
O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-567 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-567?
A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/567.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.
Fraquezas relacionadas
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