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Common Weakness Enumeration

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Home > CWE List > CWE-638: Not Using Complete Mediation (4.16)  
ID

CWE-638: Not Using Complete Mediation

Weakness ID: 638
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 does not perform access checks on a resource every time the resource is accessed by an entity, which can create resultant weaknesses if that entity's rights or privileges change over time.
+ 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.
Scope Impact Likelihood
Integrity
Confidentiality
Availability
Access Control
Other

Technical Impact: Gain Privileges or Assume Identity; Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Read Application Data; Other

A user might retain access to a critical resource even after privileges have been revoked, possibly allowing access to privileged functionality or sensitive information, depending on the role of the resource.
+ Potential Mitigations

Phase: Architecture and Design

Invalidate cached privileges, file handles or descriptors, or other access credentials whenever identities, processes, policies, roles, capabilities or permissions change. Perform complete authentication checks before accepting, caching and reusing data, dynamic content and code (scripts). Avoid caching access control decisions as much as possible.

Phase: Architecture and Design

Identify all possible code paths that might access sensitive resources. If possible, create and use a single interface that performs the access checks, and develop code standards that require use of this interface.
+ 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" (CWE-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. 657 Violation of Secure Design Principles
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. 862 Missing Authorization
ParentOf 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. 424 Improper Protection of Alternate Path
+ 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
Implementation
Operation
+ 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)

+ Demonstrative Examples

Example 1

When executable library files are used on web servers, which is common in PHP applications, the developer might perform an access check in any user-facing executable, and omit the access check from the library file itself. By directly requesting the library file (CWE-425), an attacker can bypass this access check.


Example 2

When a developer begins to implement input validation for a web application, often the validation is performed in each area of the code that uses externally-controlled input. In complex applications with many inputs, the developer often misses a parameter here or a cookie there. One frequently-applied solution is to centralize all input validation, store these validated inputs in a separate data structure, and require that all access of those inputs must be through that data structure. An alternate approach would be to use an external input validation framework such as Struts, which performs the validation before the inputs are ever processed by the code.


+ Observed Examples
Reference Description
Server does not properly validate client certificates when reusing cached connections.
+ Weakness Ordinalities
Ordinality Description
Primary
(where the weakness exists independent of other weaknesses)
+ 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. 988 SFP Secondary Cluster: Race Condition Window
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1368 ICS Dependencies (& Architecture): External Digital Systems
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1418 Comprehensive Categorization: Violation of Secure Design Principles
+ 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
+ Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
Software Fault Patterns SFP20 Race Condition Window
+ References
[REF-196] Jerome H. Saltzer and Michael D. Schroeder. "The Protection of Information in Computer Systems". Proceedings of the IEEE 63. 1975-09. <http://web.mit.edu/Saltzer/www/publications/protection/>.
[REF-526] Sean Barnum and Michael Gegick. "Complete Mediation". 2005-09-12. <https://web.archive.org/web/20221006191503/https://www.cisa.gov/uscert/bsi/articles/knowledge/principles/complete-mediation>. URL validated: 2023-04-07.
+ Content History
+ Submissions
Submission Date Submitter Organization
2008-01-18
(CWE Draft 8, 2008-01-30)
Pascal Meunier Purdue University
+ Modifications
Modification Date Modifier Organization
2008-07-01 Eric Dalci Cigital
updated Time_of_Introduction
2008-09-08 CWE Content Team MITRE
updated Common_Consequences, Relationships, Observed_Example, Weakness_Ordinalities
2009-01-12 CWE Content Team MITRE
updated Description, Name
2009-05-27 CWE Content Team MITRE
updated Related_Attack_Patterns
2010-12-13 CWE Content Team MITRE
updated Name
2011-06-01 CWE Content Team MITRE
updated Common_Consequences, Relationships
2012-05-11 CWE Content Team MITRE
updated Relationships
2012-10-30 CWE Content Team MITRE
updated Potential_Mitigations
2014-07-30 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2017-11-08 CWE Content Team MITRE
updated Applicable_Platforms, Causal_Nature
2020-02-24 CWE Content Team MITRE
updated Relationships
2022-10-13 CWE Content Team MITRE
updated References
2023-01-31 CWE Content Team MITRE
updated Description, Relationships
2023-04-27 CWE Content Team MITRE
updated References, Relationships, Time_of_Introduction
2023-06-29 CWE Content Team MITRE
updated Mapping_Notes
2023-10-26 CWE Content Team MITRE
updated Demonstrative_Examples
+ Previous Entry Names
Change Date Previous Entry Name
2009-01-12 Design Principle Violation: Not Using Complete Mediation
2010-12-13 Failure to Use Complete Mediation
Page Last Updated: November 19, 2024