CAPEC-1: Accessing Functionality Not Properly Constrained by ACLs

Overview

CAPEC-1 (Accessing Functionality Not Properly Constrained by ACLs) is a standard-level attack pattern catalogued by MITRE in the Common Attack Pattern Enumeration and Classification (CAPEC). It describes a recurring method attackers use to exploit software weaknesses.

How the attack works

The phases an attacker typically follows to carry out this attack.

Step 1
Explore
[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
Step 2
Explore
[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.
Step 3
Experiment
[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)

What the attacker needs

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

Low skill: 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

What a successful CAPEC-1 attack can achieve.

Gain Privileges

Affects: Confidentiality, Access Control, Authorization

How to mitigate it

Defenses that reduce the risk of CAPEC-1.

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.

Examples

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.

Terminology & mappings

Mapped taxonomies

ATTACK: Hijack Execution Flow: ServicesFile Permissions Weakness (1574.010)

Frequently asked questions

Common questions about CAPEC-1.

What is CAPEC-1?

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.

How does a Accessing Functionality Not Properly Constrained by ACLs attack work?

It typically unfolds over 3 phases. It begins with: [Survey] The attacker surveys the target application, possibly as a valid and authenticated user

How do you prevent CAPEC-1?

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.

What weaknesses does CAPEC-1 target?

CAPEC-1 exploits 16 CWE weaknesses, including CWE-276 (Incorrect Default Permissions), CWE-285 (Improper Authorization), CWE-434 (Unrestricted Upload of File with Dangerous Type), CWE-693 (Protection Mechanism Failure).

How severe is CAPEC-1?

MITRE rates CAPEC-1 as High severity with high likelihood of attack.

References

Attack-pattern data is sourced from the MITRE CAPEC catalog (v3.9). Weakness associations link to the corresponding CWE entries on RadicalNotion.AI.

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CAPEC-1: Accessing Functionality Not Properly Constrained by ACLs

Overview

How the attack works

The phases an attacker typically follows to carry out this attack.

Step 1
Explore
[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
Step 2
Explore
[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.
Step 3
Experiment
[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)

What the attacker needs

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

Low skill: 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

What a successful CAPEC-1 attack can achieve.

Gain Privileges

Affects: Confidentiality, Access Control, Authorization

How to mitigate it

Defenses that reduce the risk of CAPEC-1.

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.

Examples

Terminology & mappings

Mapped taxonomies

ATTACK: Hijack Execution Flow: ServicesFile Permissions Weakness (1574.010)

Frequently asked questions

Common questions about CAPEC-1.

What is CAPEC-1?

How does a Accessing Functionality Not Properly Constrained by ACLs attack work?

It typically unfolds over 3 phases. It begins with: [Survey] The attacker surveys the target application, possibly as a valid and authenticated user

How do you prevent CAPEC-1?

What weaknesses does CAPEC-1 target?

How severe is CAPEC-1?

MITRE rates CAPEC-1 as High severity with high likelihood of attack.

References

Attack-pattern data is sourced from the MITRE CAPEC catalog (v3.9). Weakness associations link to the corresponding CWE entries on RadicalNotion.AI.

Defend against CAPEC-1

Track the CVEs and weaknesses attackers exploit with this technique, with AI-written analysis and remediation guidance.

Start free See pricing

Overview

How the attack works

What the attacker needs

Prerequisites

Skills required

Resources required

Consequences

How to mitigate it

Examples

Related weaknesses

Related attack patterns

Parent

Child

Can precede

Terminology & mappings

Mapped taxonomies

Frequently asked questions

What is CAPEC-1?

How does a Accessing Functionality Not Properly Constrained by ACLs attack work?

How do you prevent CAPEC-1?

What weaknesses does CAPEC-1 target?

How severe is CAPEC-1?

References

Defend against CAPEC-1

Overview

How the attack works

What the attacker needs

Prerequisites

Skills required

Resources required

Consequences

How to mitigate it

Examples

Related weaknesses

Related attack patterns

Parent

Child

Can precede

Terminology & mappings

Mapped taxonomies

Frequently asked questions

What is CAPEC-1?

How does a Accessing Functionality Not Properly Constrained by ACLs attack work?

How do you prevent CAPEC-1?

What weaknesses does CAPEC-1 target?

How severe is CAPEC-1?

References

Defend against CAPEC-1