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Home > CWE List > CWE-441: Unintended Proxy or Intermediary ('Confused Deputy') (4.18)
ID
CWE Glossary Definition

CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')

Weakness ID: 441
Vulnerability Mapping: ALLOWED This CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review (with careful review of mapping notes)
Abstraction: Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
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Description
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.
Extended Description

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.
Alternate Terms
Confused Deputy
This weakness is sometimes referred to as the "Confused deputy" problem, in which an attacker misused the authority of one victim (the "confused deputy") when targeting another victim.
Common Consequences
Section HelpThis table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Impact Details

Gain Privileges or Assume Identity; Hide Activities; Execute Unauthorized Code or Commands

Scope: Non-Repudiation, Access Control

Potential Mitigations
Phase(s) Mitigation

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.
Relationships
Section Help This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (View-1000)
Nature Type ID Name
ChildOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 610 Externally Controlled Reference to a Resource in Another Sphere
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 918 Server-Side Request Forgery (SSRF)
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 1021 Improper Restriction of Rendered UI Layers or Frames
PeerOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 611 Improper Restriction of XML External Entity Reference
CanPrecede Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 668 Exposure of Resource to Wrong Sphere
Relevant to the view "Architectural Concepts" (View-1008)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1014 Identify Actors
Relevant to the view "Hardware Design" (View-1194)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1198 Privilege Separation and Access Control Issues
Modes Of Introduction
Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase Note
Architecture and Design REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Applicable Platforms
Section HelpThis listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages

Class: Not Language-Specific (Undetermined Prevalence)

Operating Systems

Class: Not OS-Specific (Undetermined Prevalence)

Architectures

Class: Not Architecture-Specific (Undetermined Prevalence)

Technologies

Class: Not Technology-Specific (Undetermined Prevalence)

Demonstrative Examples

Example 1


A SoC contains a microcontroller (running ring-3 (least trusted ring) code), a Memory Mapped Input Output (MMIO) mapped IP core (containing design-house secrets), and a Direct Memory Access (DMA) controller, among several other compute elements and peripherals. The SoC implements access control to protect the registers in the IP core (which registers store the design-house secrets) from malicious, ring-3 (least trusted ring) code executing on the microcontroller. The DMA controller, however, is not blocked off from accessing the IP core for functional reasons.

(bad code)
Example Language: Other
The code in ring-3 (least trusted ring) of the microcontroller attempts to directly read the protected registers in IP core through MMIO transactions. However, this attempt is blocked due to the implemented access control. Now, the microcontroller configures the DMA core to transfer data from the protected registers to a memory region that it has access to. The DMA core, which is acting as an intermediary in this transaction, does not preserve the identity of the microcontroller and, instead, initiates a new transaction with its own identity. Since the DMA core has access, the transaction (and hence, the attack) is successful.

The weakness here is that the intermediary or the proxy agent did not ensure the immutability of the identity of the microcontroller initiating the transaction.

(good code)
Example Language: Other
The DMA core forwards this transaction with the identity of the code executing on the microcontroller, which is the original initiator of the end-to-end transaction. Now the transaction is blocked, as a result of forwarding the identity of the true initiator which lacks the permission to access the confidential MMIO mapped IP core.


Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
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.
RPC portmapper could redirect service requests from an attacker to another entity, which thinks the requests came from the portmapper.
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.
Web server allows attackers to request a URL from another server, including other ports, which allows proxied scanning.
CGI script accepts and retrieves incoming URLs.
Bounce attack allows access to TFTP from trusted side.
Web-based mail program allows internal network scanning using a modified POP3 port number.
URL-downloading library automatically follows redirects to file:// and scp:// URLs
Detection Methods
Method Details

Automated Static Analysis
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.)

Effectiveness: High
Memberships
Section HelpThis MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature Type ID Name
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 956 SFP Secondary Cluster: Channel Attack
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1345 OWASP Top Ten 2021 Category A01:2021 - Broken Access Control
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1396 Comprehensive Categorization: Access Control
Vulnerability Mapping Notes
Usage ALLOWED-WITH-REVIEW
(this CWE ID could be used to map to real-world vulnerabilities in limited situations requiring careful review)
Reason Abstraction

Rationale

This CWE entry is a Class and might have Base-level children that would be more appropriate

Comments

Examine children of this entry to see if there is a better fit
Notes

Relationship

This weakness has a chaining relationship with CWE-668 (Exposure of Resource to Wrong Sphere) because the proxy effectively provides the attacker with access to the target's resources that the attacker cannot directly obtain.

Theoretical

It could be argued that the "confused deputy" is a fundamental aspect of most vulnerabilities that require an active attacker. Even for common implementation issues such as buffer overflows, SQL injection, OS command injection, and path traversal, the vulnerable program already has the authorization to run code or access files. The vulnerability arises when the attacker causes the program to run unexpected code or access unexpected files.

Maintenance

This could possibly be considered as an emergent resource.
Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Unintended proxy/intermediary
PLOVER Proxied Trusted Channel
WASC 32 Routing Detour
References
[REF-432] Norm Hardy. "The Confused Deputy (or why capabilities might have been invented)". 1988.
<http://www.cap-lore.com/CapTheory/ConfusedDeputy.html>.
[REF-1125] moparisthebest. "Validation Vulnerabilities". 2015年06月05日.
<https://mailarchive.ietf.org/arch/msg/acme/s6Q5PdJP48LEUwgzrVuw_XPKCsM/>.
Content History
Submissions
Submission Date Submitter Organization
2006年07月19日
(CWE Draft 3, 2006年07月19日) 		PLOVER
Contributions
Contribution Date Contributor Organization
2020年08月14日 Arun Kanuparthi, Hareesh Khattri, Parbati K. Manna Intel Corporation
Provided demonstrative example
Modifications
Modification Date Modifier Organization
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes
2023年04月27日 CWE Content Team MITRE
updated Detection_Factors, Relationships
2022年10月13日 CWE Content Team MITRE
updated Related_Attack_Patterns
2021年10月28日 CWE Content Team MITRE
updated Relationships
2020年08月20日 CWE Content Team MITRE
updated Applicable_Platforms, Common_Consequences, Demonstrative_Examples, Description, Potential_Mitigations, References, Relationships
2020年08月14日 CWE Content Team MITRE
Per Intel Corporation suggestion, added language to be inclusive to hardware: updated Demonstrative_Examples, Description, Extended_Description, Applicable_Platforms, Potential_Mitigation, Common_Consequences, References
2020年02月24日 CWE Content Team MITRE
updated Relationships
2019年06月20日 CWE Content Team MITRE
updated Relationships
2017年11月08日 CWE Content Team MITRE
updated Modes_of_Introduction, Relationships
2017年01月19日 CWE Content Team MITRE
updated Relationships
2015年12月07日 CWE Content Team MITRE
updated Relationships
2014年07月30日 CWE Content Team MITRE
updated Relationships
2013年02月21日 CWE Content Team MITRE
updated Alternate_Terms, Applicable_Platforms, Description, Maintenance_Notes, Name, Observed_Examples, References, Relationship_Notes, Relationships, Theoretical_Notes, Type
2012年10月30日 CWE Content Team MITRE
updated Potential_Mitigations
2012年05月11日 CWE Content Team MITRE
updated Related_Attack_Patterns, Relationships
2011年06月27日 CWE Content Team MITRE
updated Common_Consequences
2011年06月01日 CWE Content Team MITRE
updated Common_Consequences
2010年06月21日 CWE Content Team MITRE
updated Other_Notes
2010年04月05日 CWE Content Team MITRE
updated Related_Attack_Patterns
2010年02月16日 CWE Content Team MITRE
updated Taxonomy_Mappings
2008年11月24日 CWE Content Team MITRE
updated Maintenance_Notes, Relationships, Taxonomy_Mappings, Time_of_Introduction
2008年09月08日 CWE Content Team MITRE
updated Relationships, Observed_Example, Other_Notes, Taxonomy_Mappings
2008年07月01日 Eric Dalci Cigital
updated Potential_Mitigations, Time_of_Introduction
Previous Entry Names
Change Date Previous Entry Name
2013年02月21日 Unintended Proxy/Intermediary
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Page Last Updated: September 09, 2025

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