CWE-441: 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.
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 table(s) below 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" (CWE-1000)
Relevant to the view "Hardware Design" (CWE-1194)
Relevant to the view "Architectural Concepts" (CWE-1008)
The 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.
The listings below show 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.
Class: Language-Independent (Undetermined Prevalence)
Class: OS-Independent (Undetermined Prevalence)
Class: Architecture-Independent (Undetermined Prevalence)
Class: Technology-Independent (Undetermined Prevalence)
The table below 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.
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.
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.
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.
This 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.
This could possibly be considered as an emergent resource.
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.
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.
More information is available — Please select a different filter.