What is CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')?+
CWE-441: Unintended Proxy or Intermediary ('Confused Deputy') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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. If an attacker cannot directly contact a target, but the product has access to the target, then the attacker can send a request to the product and have it be forwarded to the target. The request would appear to be coming from the product's system, not the attacker's system. As a result, the attacker can bypass access controls (such as firewalls) or hide the source of malicious requests, since the requests would not be coming directly from the attacker. Since proxy functionality and message-forwarding often serve a legitimate purpose, this issue only becomes a vulnerability when: 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.
What are the security consequences of Unintended Proxy or Intermediary ('Confused Deputy')?+
If exploited, CWE-441 (Unintended Proxy or Intermediary ('Confused Deputy')) it can compromise Non-Repudiation and Access Control, leading to outcomes such as Gain Privileges or Assume Identity, Hide Activities and Execute Unauthorized Code or Commands.
How do you prevent or mitigate Unintended Proxy or Intermediary ('Confused Deputy')?+
Recommended mitigations for CWE-441 include: Enforce the use of strong mutual authentication mechanism between the two parties. 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.
Which programming languages are affected by Unintended Proxy or Intermediary ('Confused Deputy')?+
CWE-441 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
What are real-world examples of Unintended Proxy or Intermediary ('Confused Deputy')?+
MITRE documents real CVEs mapped to CWE-441, including CVE-1999-0017, CVE-1999-0168, CVE-2005-0315, CVE-2002-1484 and CVE-2004-2061. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
What is the difference between a CWE and a CVE?+
A CWE (Common Weakness Enumeration) like CWE-441 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.