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

Opis

The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

HTTP requests or responses ("messages") can be malformed or unexpected in ways that cause web servers or clients to interpret the messages in different ways than intermediary HTTP agents such as load balancers, reverse proxies, web caching proxies, application firewalls, etc. For example, an adversary may be able to add duplicate or different header fields that a client or server might interpret as one set of messages, whereas the intermediary might interpret the same sequence of bytes as a different set of messages. For example, discrepancies can arise in how to handle duplicate headers like two Transfer-encoding (TE) or two Content-length (CL), or the malicious HTTP message will have different headers for TE and CL.

The inconsistent parsing and interpretation of messages can allow the adversary to "smuggle" a message to the client/server without the intermediary being aware of it.

This weakness is usually the result of the usage of outdated or incompatible HTTP protocol versions in the HTTP agents.

Inne nazwy

HTTP Request Smuggling

HTTP Response Smuggling

HTTP Smuggling

Skutki

• Integrity, Non-Repudiation, Access Control

  Unexpected State; Hide Activities; Bypass Protection Mechanism

  An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).

Zapobieganie

• 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.

Przykłady podatności

• 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

Słabość nadrzędna

• CWE-436 Interpretation Conflict

Kiedy powstaje

• Implementation

Dotyczy

Not Language-Specific, Web Based, Web Server

Uwagi

Request smuggling can be performed due to a multiple interpretation error, where the target is an intermediary or monitor, via a consistency manipulation (Transfer-Encoding and Content-Length headers).

Źródła

1. HTTP Request Smuggling — Chaim Linhart, Amit Klein, Ronen Heled, Steve Orrin
2. HTTP Response Smuggling — Robert Auger, 2011
3. HTTP Request Smuggling: Complete Guide to Attack Types and Prevention — Dzevad Alibegovic, 2021
4. A Pentester's Guide to HTTP Request Smuggling — Busra Demir, 2020
5. HTTP Desync Attacks in the Wild and How to Defend Against Them — Edi Kogan, Daniel Kerman, 2019
6. HTTP Desync Attacks: Request Smuggling Reborn — James Kettle, 2019
7. HTTP request smuggling — PortSwigger