An attacker manipulates the headers and content of an email message by injecting data via the use of delimiter characters native to the protocol. Many applications allow users to send email messages by filling in fields. For example, a web site may have a link to "share this site with a friend" where the user provides the recipient's email address and the web application fills out all the other fields, such as the subject and body. In this pattern, an attacker adds header and body information to an email message by injecting additional content in an input field used to construct a header of the mail message. This attack takes advantage of the fact that RFC 822 requires that headers in a mail message be separated by a carriage return. As a result, an attacker can inject new headers or content simply by adding a delimiting carriage return and then supplying the new heading and body information. This attack will not work if the user can only supply the message body since a carriage return in the body is treated as a normal character.
The table below 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.
Meta 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.
Detailed 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.
The target application must allow the user to send email to some recipient, to specify the content at least one header field in the message, and must fail to sanitize against the injection of command separators.
The adversary must have the ability to access the target mail application.
None: No specialized resources are required to execute this type of attack.
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.
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Page Last Updated or Reviewed:
September 30, 2019