CWE-441

ClassDraft

Unintended Proxy or Intermediary ('Confused Deputy')

The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.

28 linked vulnerabilities

2 related weaknesses

Extended Description

The product runs with different privileges or on a different system, or otherwise has different levels of access than the upstream component;
The attacker is prevented from making the request directly to the target; and
The attacker can create a request that the proxy does not explicitly intend to be forwarded on the behalf of the requester. Such a request might point to an unexpected hostname, port number, hardware IP, or service. Or, the request might be sent to an allowed service, but the request could contain disallowed directives, commands, or resources.

Architecture and Design

Enforce the use of strong mutual authentication mechanism between the two parties.

Architecture and Design

Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.

Non-RepudiationAccess ControlGain Privileges or Assume IdentityHide ActivitiesExecute Unauthorized Code or Commands

Automated Static AnalysisEffectiveness: High

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.)

Modes of Introduction

Architecture and Design

Related Weaknesses

CWE-610ChildOf CWE-668CanPrecede

Example CVEs (8)

CVE-1999-0017

FTP bounce attack. The design of the protocol allows an attacker to modify the PORT command to cause the FTP server to connect to other machines besides the attacker's.

CVE-1999-0168

RPC portmapper could redirect service requests from an attacker to another entity, which thinks the requests came from the portmapper.

CVE-2005-0315

FTP server does not ensure that the IP address in a PORT command is the same as the FTP user's session, allowing port scanning by proxy.

CVE-2002-1484

Web server allows attackers to request a URL from another server, including other ports, which allows proxied scanning.

CVE-2004-2061

CGI script accepts and retrieves incoming URLs.