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CAPEC-1: Accessing Functionality Not Properly Constrained by ACLs

Attack Pattern ID: 1
Abstraction: Standard
Status: Draft
Presentation Filter:
+ Description
In applications, particularly web applications, access to functionality is mitigated by an authorization framework. This framework maps Access Control Lists (ACLs) to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application, or can run queries for data that they otherwise not supposed to.
+ Likelihood Of Attack


+ Typical Severity


+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
ChildOfMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.122Privilege Abuse
ParentOfDetailed Attack PatternDetailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.58Restful Privilege Elevation
CanPrecedeStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.17Using Malicious Files
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
  1. Survey: The attacker surveys the target application, possibly as a valid and authenticated user

    Spidering web sites for all available links
    Brute force guessing of resource names
    Brute force guessing of user names / credentials
    Brute force guessing of function names / actions
  2. Identify Functionality: At each step, the attacker notes the resource or functionality access mechanism invoked upon performing specific actions

    Use the web inventory of all forms and inputs and apply attack data to those inputs.
    Use a packet sniffer to capture and record network traffic
    Execute the software in a debugger and record API calls into the operating system or important libraries. This might occur in an environment other than a production environment, in order to find weaknesses that can be exploited in a production environment.
  1. Iterate over access capabilities: Possibly as a valid user, the attacker then tries to access each of the noted access mechanisms directly in order to perform functions not constrained by the ACLs.

    Fuzzing of API parameters (URL parameters, OS API parameters, protocol parameters)
+ Prerequisites
The application must be navigable in a manner that associates elements (subsections) of the application with ACLs.
The various resources, or individual URLs, must be somehow discoverable by the attacker
The administrator must have forgotten to associate an ACL or has associated an inappropriately permissive ACL with a particular navigable resource.
+ Skills Required
[Level: Low]
In order to discover unrestricted resources, the attacker does not need special tools or skills. They only have to observe the resources or access mechanisms invoked as each action is performed and then try and access those access mechanisms directly.
+ Resources Required
None: No specialized resources are required to execute this type of attack.
+ Consequences
Section HelpThis table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. 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 pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Access Control
Gain Privileges
+ Mitigations

In a J2EE setting, administrators can associate a role that is impossible for the authenticator to grant users, such as "NoAccess", with all Servlets to which access is guarded by a limited number of servlets visible to, and accessible by, the user.

Having done so, any direct access to those protected Servlets will be prohibited by the web container.

In a more general setting, the administrator must mark every resource besides the ones supposed to be exposed to the user as accessible by a role impossible for the user to assume. The default security setting must be to deny access and then grant access only to those resources intended by business logic.

+ Example Instances

Implementing the Model-View-Controller (MVC) within Java EE's Servlet paradigm using a "Single front controller" pattern that demands that brokered HTTP requests be authenticated before hand-offs to other Action Servlets.

If no security-constraint is placed on those Action Servlets, such that positively no one can access them, the front controller can be subverted.

+ Taxonomy Mappings
Relevant to the ATT&CK taxonomy mapping
Entry IDEntry Name
1574.010Hijack Execution Flow: ServicesFile Permissions Weakness
+ Content History
Submission DateSubmitterOrganization
2014-06-23CAPEC Content TeamThe MITRE Corporation
Modification DateModifierOrganization
2017-05-01CAPEC Content TeamThe MITRE Corporation
Updated Attack_Pattern, References
2017-08-04CAPEC Content TeamThe MITRE Corporation
Updated Attack_Pattern, Description Summary
2020-07-30CAPEC Content TeamThe MITRE Corporation
Updated Related_Weaknesses, Skills_Required, Taxonomy_Mappings
2020-12-17CAPEC Content TeamThe MITRE Corporation
Updated Related_Attack_Patterns, Related_Weaknesses
2021-06-24CAPEC Content TeamThe MITRE Corporation
Updated Related_Weaknesses
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Page Last Updated or Reviewed: December 17, 2020