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CAPEC-4: Using Alternative IP Address Encodings

Attack Pattern ID: 4
Abstraction: Detailed
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+ Description
This attack relies on the adversary using unexpected formats for representing IP addresses. Networked applications may expect network location information in a specific format, such as fully qualified domains names (FQDNs), URL, IP address, or IP Address ranges. If the location information is not validated against a variety of different possible encodings and formats, the adversary can use an alternate format to bypass application access control.
+ 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.
ChildOfStandard 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.267Leverage Alternate Encoding
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
  1. Survey the application for IP addresses as user input: Using a browser, an automated tool or by inspecting the application, an adversary records all entry points to the application where IP addresses are used.

    Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL.
    Use a proxy tool to record all user input entry points visited during a manual traversal of the web application.
    Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery.
    Manually inspect the application to find entry points.
  1. Probe entry points to locate vulnerabilities: The adversary uses the entry points gathered in the "Explore" phase as a target list and attempts alternate IP address encodings, observing application behavior. The adversary will also attempt to access the application through an alternate IP address encoding to see if access control changes

    Instead of using a URL, use the IP address that the URL resolves to
    Specify a port directly to a URL input
    Omit or add "http://" or "https://" to a URL to see if the application behaves differently
  1. Bypass access control: Using an alternate IP address encoding, the adversary will either access the application or give the alternate encoding as input, bypassing access control restrictions.

+ Prerequisites
The target software must fail to anticipate all of the possible valid encodings of an IP/web address.
The adversary must have the ability to communicate with the server.
+ Skills Required
[Level: Low]
The adversary has only to try IP address format combinations.
+ Resources Required
The adversary needs to have knowledge of an alternative IP address encoding that bypasses the access control policy of an application. Alternatively, the adversary can simply try to brute-force various encoding possibilities.
+ 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
Design: Default deny access control policies
Design: Input validation routines should check and enforce both input data types and content against a positive specification. In regards to IP addresses, this should include the authorized manner for the application to represent IP addresses and not accept user specified IP addresses and IP address formats (such as ranges)
Implementation: Perform input validation for all remote content.
+ Example Instances
An adversary identifies an application server that applies a security policy based on the domain and application name. For example, the access control policy covers authentication and authorization for anyone accessing http://example.domain:8080/application. However, by using the IP address of the host instead (, the application authentication and authorization controls may be bypassed. The adversary relies on the victim applying policy to the namespace abstraction and not having a default deny policy in place to manage exceptions.
+ Taxonomy Mappings
Section HelpCAPEC mappings to ATT&CK techniques leverage an inheritance model to streamline and minimize direct CAPEC/ATT&CK mappings. Inheritance of a mapping is indicated by text stating that the parent CAPEC has relevant ATT&CK mappings. Note that the ATT&CK Enterprise Framework does not use an inheritance model as part of the mapping to CAPEC.
Relevant to the ATT&CK taxonomy mapping (see parent )
+ References
[REF-1] G. Hoglund and G. McGraw. "Exploiting Software: How to Break Code". Addison-Wesley. 2004-02.
+ Content History
Submission DateSubmitterOrganization
(Version 2.6)
CAPEC Content TeamThe MITRE Corporation
Modification DateModifierOrganization
(Version 2.11)
CAPEC Content TeamThe MITRE Corporation
Updated Attack_Prerequisites, Attacker_Skills_or_Knowledge_Required, Description Summary, Examples-Instances, Resources_Required
(Version 3.1)
CAPEC Content TeamThe MITRE Corporation
Updated Related_Weaknesses
(Version 3.7)
CAPEC Content TeamThe MITRE Corporation
Updated Description, Execution_Flow
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Page Last Updated or Reviewed: July 31, 2018