The product uses a web-client protection mechanism such as a Content Security Policy (CSP) or cross-domain policy file, but the policy includes untrusted domains with which the web client is allowed to communicate.

If a cross-domain policy file includes domains that should not be trusted, such as when using wildcards under a high-level domain, then the application could be attacked by these untrusted domains. In many cases, the attack can be launched without the victim even being aware of it.

This 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

Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Read Application Data; Varies by Context

Scope: Confidentiality, Integrity, Availability, Access Control With an overly permissive policy file, an attacker may be able to bypass the web browser's same-origin policy and conduct many of the same attacks seen in Cross-Site Scripting (CWE-79). An attacker can exploit the weakness to transfer private information from the victim's machine to the attacker, manipulate or steal cookies that may include session information, create malicious requests to a web site on behalf of the victim, or execute malicious code on the end user systems. Other damaging attacks include the disclosure of end user files, installation of Trojan horse programs, redirecting the user to some other page or site, running ActiveX controls (under Microsoft Internet Explorer) from sites that a user perceives as trustworthy, and modifying presentation of content.

Phase(s)	Mitigation
Architecture and Design; Operation	Strategy: Attack Surface Reduction Define a restrictive Content Security Policy [REF-1486] or cross-domain policy file.
Architecture and Design; Operation	Strategy: Attack Surface Reduction Avoid using wildcards in the CSP / cross-domain policy file. Any domain matching the wildcard expression will be implicitly trusted, and can perform two-way interaction with the target server.
Architecture and Design; Operation	Strategy: Environment Hardening For Flash, modify crossdomain.xml to use meta-policy options such as 'master-only' or 'none' to reduce the possibility of an attacker planting extraneous cross-domain policy files on a server.

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.

In HTTP/HTTPS, policies such as the Same Origin Policy prevent web clients from loading resources from (or making requests to) domains that did not match the web site's own domain, e.g., Javascript or other code hosted on third-party servers. These policies are strictly enforced by browsers and other products. However, these restrictions can be reduced using mechanisms that specify other domains that are allowed to be contacted from the original site, such as Content Security Policy (CSP) or cross-domain policy files (e.g., "crossdomain.xml" in Adobe Flash or Reader, "clientaccesspolicy.xml" in Silverlight, etc.). These mechanisms define a list of domains from which a client is allowed to make cross-domain requests. When making a cross-domain request, the client will first look for the policy file on the target server. If it is found, and the domain hosting the application is explicitly allowed to make requests, the request is made.

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.

Phase	Note
Implementation
Architecture and Design	COMMISSION: This weakness refers to an incorrect design related to an architectural security tactic.

This 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)
Technologies	Class: Web Based (Undetermined Prevalence) Web Server (Undetermined Prevalence)

Example 1

These cross-domain policy files mean to allow Flash and Silverlight applications hosted on other domains to access its data:

Flash crossdomain.xml :

Silverlight clientaccesspolicy.xml :

These entries are far too permissive, allowing any Flash or Silverlight application to send requests. A malicious application hosted on any other web site will be able to send requests on behalf of any user tricked into executing it.

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.

Ordinality	Description
Primary	(where the weakness exists independent of other weaknesses)

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

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.

Usage	ALLOWED (this CWE ID may be used to map to real-world vulnerabilities)
Reason	Acceptable-Use
Rationale	This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comments	Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

[REF-1486]	OWASP. "Content Security Policy Cheat Sheet". <https://cheatsheetseries.owasp.org/cheatsheets/Content_Security_Policy_Cheat_Sheet.html>. (URL validated: 2025-09-08)
[REF-943]	Apurva Udaykumar. "Setting a crossdomain.xml file for HTTP streaming". Adobe. 2012-11-19. <https://web.archive.org/web/20121124184922/http://www.adobe.com/devnet/adobe-media-server/articles/cross-domain-xml-for-streaming.html>. (URL validated: 2023-04-07)
[REF-944]	Adobe. "Cross-domain policy for Flash movies". Adobe. <http://kb2.adobe.com/cps/142/tn_14213.html>.
[REF-945]	Microsoft Corporation. "HTTP Communication and Security with Silverlight". <https://learn.microsoft.com/en-us/previous-versions/windows/silverlight/dotnet-windows-silverlight/cc838250(v=vs.95)?redirectedfrom=MSDN>. (URL validated: 2023-04-07)
[REF-946]	Microsoft Corporation. "Network Security Access Restrictions in Silverlight". <https://learn.microsoft.com/en-us/previous-versions/windows/silverlight/dotnet-windows-silverlight/cc645032(v=vs.95)>. (URL validated: 2023-04-07)
[REF-947]	Dongseok Jang, Aishwarya Venkataraman, G. Michael Sawka and Hovav Shacham. "Analyzing the Crossdomain Policies of Flash Applications". 2011-05. <http://cseweb.ucsd.edu/~hovav/dist/crossdomain.pdf>.

Submissions
Submission Date	Submitter	Organization
2014-06-05 (CWE 2.7, 2014-06-23)	CWE Content Team	MITRE
	Created by MITRE with input from members of the CWE-Research mailing list.
Contributions
Contribution Date	Contributor	Organization
2022-08-23 (CWE 4.18, 2025-09-09)	Jagjeet Singh	Rakuten Kobo Inc.
	Suggested new entry for misconfigured CSP allowing JavaScript, leading to changes in CWE-942 to make it more general
Modifications
Modification Date	Modifier	Organization
2025-12-11 (CWE 4.19, 2025-12-11)	CWE Content Team	MITRE
	updated Applicable_Platforms, Relationships, Weakness_Ordinalities
2025-09-09 (CWE 4.18, 2025-09-09)	CWE Content Team	MITRE
	updated Background_Details, Common_Consequences, Description, Name, Potential_Mitigations, References
2024-02-29 (CWE 4.14, 2024-02-29)	CWE Content Team	MITRE
	updated Demonstrative_Examples
2023-06-29 (CWE 4.12, 2023-06-29)	CWE Content Team	MITRE
	updated Mapping_Notes, Relationships
2023-04-27 (CWE 4.11, 2023-04-27)	CWE Content Team	MITRE
	updated Detection_Factors, References, Relationships
2023-01-31 (CWE 4.10, 2023-01-31)	CWE Content Team	MITRE
	updated Description, Relationships
2021-10-28 (CWE 4.6, 2021-10-28)	CWE Content Team	MITRE
	updated Relationships
2020-06-25 (CWE 4.1, 2020-06-25)	CWE Content Team	MITRE
	updated Description, Name
2020-02-24 (CWE 4.0, 2020-02-24)	CWE Content Team	MITRE
	updated Applicable_Platforms, Relationships
2019-06-20 (CWE 3.3, 2019-06-20)	CWE Content Team	MITRE
	updated Relationships
2017-11-08 (CWE 3.0, 2017-11-08)	CWE Content Team	MITRE
	updated Modes_of_Introduction, References, Relationships
Previous Entry Names
Change Date	Previous Entry Name
2025-09-09	Permissive Cross-domain Policy with Untrusted Domains
2020-02-26	Overly Permissive Cross-domain Whitelist