CWE-444 Base Incompleto

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

This weakness occurs when a proxy, firewall, or other intermediary HTTP agent interprets a malformed HTTP request or response differently than the final destination server or client. This…

Definição

What is CWE-444?

This weakness occurs when a proxy, firewall, or other intermediary HTTP agent interprets a malformed HTTP request or response differently than the final destination server or client. This inconsistency allows an attacker to craft messages that bypass the intermediary's security checks.
HTTP request smuggling exploits differences in how web servers, clients, and intermediary devices (like load balancers, reverse proxies, or WAFs) parse ambiguous HTTP messages. An attacker can inject conflicting headers—such as duplicate `Content-Length` or `Transfer-Encoding` fields—causing the intermediary and the backend server to see two different requests or responses in the same network stream. This lets malicious traffic slip through undetected. This vulnerability typically stems from using outdated HTTP parsing libraries or mismatched protocol versions between system components. To prevent it, developers must ensure all HTTP agents in the data flow use consistent, up-to-date parsing logic and rigorously validate message formatting.
Impacto no mundo real

Real-world CVEs caused by CWE-444

  • CVE-2022-24766

    SSL/TLS-capable proxy allows HTTP smuggling when used in tandem with HTTP/1.0 services, due to inconsistent interpretation and input sanitization of HTTP messages within the body of another message

  • CVE-2021-37147

    Chain: caching proxy server has improper input validation (CWE-20) of headers, allowing HTTP response smuggling (CWE-444) using an "LF line ending"

  • CVE-2020-8287

    Node.js platform allows request smuggling via two Transfer-Encoding headers

  • CVE-2006-6276

    Web servers allow request smuggling via inconsistent HTTP headers.

  • CVE-2005-2088

    HTTP server allows request smuggling with both a "Transfer-Encoding: chunked" header and a Content-Length header

  • CVE-2005-2089

    HTTP server allows request smuggling with both a "Transfer-Encoding: chunked" header and a Content-Length header

Como os atacantes a exploram

Trajeto do atacante passo a passo

  1. 1

    In the following example, a malformed HTTP request is sent to a website that includes a proxy server and a web server with the intent of poisoning the cache to associate one webpage with another malicious webpage.

  2. 2

    When this request is sent to the proxy server, the proxy server parses the first four lines of the POST request and encounters the two "Content-Length" headers. The proxy server ignores the first header, so it assumes the request has a body of length 54 bytes. Therefore, it treats the data in the next three lines that contain exactly 54 bytes as the first request's body:

  3. 3

    The proxy then parses the remaining bytes, which it treats as the client's second request:

  4. 4

    The original request is forwarded by the proxy server to the web server. Unlike the proxy, the web server uses the first "Content-Length" header and considers that the first POST request has no body.

  5. 5

    Because the web server has assumed the original POST request was length 0, it parses the second request that follows, i.e. for GET /poison.html:

Exemplo de código vulnerável

Vulnerable code

In the following example, a malformed HTTP request is sent to a website that includes a proxy server and a web server with the intent of poisoning the cache to associate one webpage with another malicious webpage.

Vulnerável 
POST http://www.website.com/foobar.html HTTP/1.1
 Host: www.website.com
 Connection: Keep-Alive
 Content-Type: application/x-www-form-urlencoded
 Content-Length: 0
 Content-Length: 54

 GET /poison.html HTTP/1.1
 Host: www.website.com
 Bla: GET http://www.website.com/page_to_poison.html HTTP/1.1
 Host: www.website.com
 Connection: Keep-Alive
Payload do atacante

In the following example, a malformed HTTP request is sent to a website that includes a proxy server and a web server with the intent of poisoning the cache to associate one webpage with another malicious webpage.

Payload do atacante 
POST http://www.website.com/foobar.html HTTP/1.1
 Host: www.website.com
 Connection: Keep-Alive
 Content-Type: application/x-www-form-urlencoded
 Content-Length: 0
 Content-Length: 54

 GET /poison.html HTTP/1.1
 Host: www.website.com
 Bla: GET http://www.website.com/page_to_poison.html HTTP/1.1
 Host: www.website.com
 Connection: Keep-Alive
Exemplo de código seguro

Secure Java

Additionally, if a web application includes a Java servlet for processing requests, the servlet can check for multiple "Content-Length" headers and if they are found the servlet can return an error response thereby preventing the poison page to be cached, as shown below.

Seguro Java 
protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
```
// Set up response writer object* 
  		...
  		try { 
  		```
```
// check for multiple content length headers* 
  				Enumeration contentLengthHeaders = request.getHeaders("Content-Length"); 
  				int count = 0; 
  				while (contentLengthHeaders.hasMoreElements()) { 
  				```
  					count++; 
  				} 
  				if (count > 1) { 
```
// output error response* } 
  				else { 
  				```
```
// process request* } 
  				} catch (Exception ex) {...}}
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-444

  • Implementation Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433].
  • Implementation Use only SSL communication.
  • Implementation Terminate the client session after each request.
  • System Configuration Turn all pages to non-cacheable.
Sinais de deteção

How to detect CWE-444

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.

Correção automática do Plexicus

O Plexicus deteta automaticamente o CWE-444 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.

Obter uma demonstração Experimente o Plexicus gratuitamente
Perguntas frequentes

Frequently asked questions

O que é o CWE-444?

This weakness occurs when a proxy, firewall, or other intermediary HTTP agent interprets a malformed HTTP request or response differently than the final destination server or client. This inconsistency allows an attacker to craft messages that bypass the intermediary's security checks.

Qual a gravidade do CWE-444?

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-444?

MITRE lists the following affected platforms: Web Based.

Como posso prevenir o CWE-444?

Use a web server that employs a strict HTTP parsing procedure, such as Apache [REF-433]. Use only SSL communication.

Como é que o Plexicus deteta e corrige o CWE-444?

O motor SAST do Plexicus correlaciona a assinatura de fluxo de dados do CWE-444 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-444?

A MITRE publica a definição canónica em https://cwe.mitre.org/data/definitions/444.html. Pode também consultar a documentação da OWASP e do NIST para orientações adjacentes.

Fraquezas relacionadas

Weaknesses related to CWE-444

CWE-436 Pai

Interpretation Conflict

An interpretation conflict occurs when two systems process the same data or sequence of events differently, leading one system to make…

CWE-113 Irmão

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

This vulnerability occurs when an application accepts user-supplied data and includes it directly in HTTP headers without properly…

CWE-115 Irmão

Misinterpretation of Input

This vulnerability occurs when software incorrectly interprets or processes input data, leading to unintended and potentially harmful…

CWE-437 Irmão

Incomplete Model of Endpoint Features

This vulnerability occurs when a security product, proxy, or monitoring system sits between endpoints but lacks a full understanding of…

CWE-626 Irmão

Null Byte Interaction Error (Poison Null Byte)

This vulnerability occurs when software incorrectly processes null bytes (NUL characters) as data moves between different systems or…

CWE-650 Irmão

Trusting HTTP Permission Methods on the Server Side

This vulnerability occurs when a server incorrectly assumes that HTTP GET requests are always safe and cannot change server-side data.…

CWE-86 Irmão

Improper Neutralization of Invalid Characters in Identifiers in Web Pages

This vulnerability occurs when an application fails to properly filter or escape invalid characters within web identifiers like HTML tag…

Recursos

Further reading

Pronto quando você estiver

Pare de pagar por desenvolvedor.
Comece a fechar o ciclo.

O Plexicus é o ASPM nativo de IA que verifica, filtra, corrige, pentesta e explica — de forma autónoma. Programadores ilimitados, repos ilimitados, ações de IA de utilização justa. Nível gratuito real, €269/mo anual quando estiver pronto.

Começar grátis Reservar uma demo