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CAPEC-15: Command Delimiters

Attack Pattern ID: 15
Abstraction: Standard
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+ Description
An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or denylist input validation, as opposed to allowlist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or denylist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on.
+ 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.137Parameter Injection
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.460HTTP Parameter Pollution (HPP)
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
  1. Assess Target Runtime Environment: In situations where the runtime environment is not implicitly known, the attacker makes connections to the target system and tries to determine the system's runtime environment. Knowing the environment is vital to choosing the correct delimiters.

    Port mapping using network connection-based software (e.g., nmap, nessus, etc.)
    Port mapping by exploring the operating system (netstat, sockstat, etc.)
    TCP/IP Fingerprinting
    Induce errors to find informative error messages
  2. Survey the Application: The attacker surveys the target application, possibly as a valid and authenticated user

    Spidering web sites for all available links
    Inventory all application inputs
  1. Attempt delimiters in inputs: The attacker systematically attempts variations of delimiters on known inputs, observing the application's response each time.

    Inject command delimiters using network packet injection tools (netcat, nemesis, etc.)
    Inject command delimiters using web test frameworks (proxies, TamperData, custom programs, etc.)
    Enter command delimiters directly in input fields.
  1. Use malicious command delimiters: The attacker uses combinations of payload and carefully placed command delimiters to attack the software.

+ Prerequisites
Software's input validation or filtering must not detect and block presence of additional malicious command.
+ Skills Required
[Level: Medium]
The attacker has to identify injection vector, identify the specific commands, and optionally collect the output, i.e. from an interactive session.
+ Resources Required
Ability to communicate synchronously or asynchronously with server. Optionally, ability to capture output directly through synchronous communication or other method such as FTP.
+ 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.
Execute Unauthorized Commands
Read Data
+ Mitigations
Design: Perform allowlist validation against a positive specification for command length, type, and parameters.
Design: Limit program privileges, so if commands circumvent program input validation or filter routines then commands do not running under a privileged account
Implementation: Perform input validation for all remote content.
Implementation: Use type conversions such as JDBC prepared statements.
+ Example Instances

By appending special characters, such as a semicolon or other commands that are executed by the target process, the attacker is able to execute a wide variety of malicious commands in the target process space, utilizing the target's inherited permissions, against any resource the host has access to. The possibilities are vast including injection attacks against RDBMS (SQL Injection), directory servers (LDAP Injection), XML documents (XPath and XQuery Injection), and command line shells. In many injection attacks, the results are converted back to strings and displayed to the client process such as a web browser without tripping any security alarms, so the network firewall does not log any out of the ordinary behavior.

LDAP servers house critical identity assets such as user, profile, password, and group information that is used to authenticate and authorize users. An attacker that can query the directory at will and execute custom commands against the directory server is literally working with the keys to the kingdom in many enterprises. When user, organizational units, and other directory objects are queried by building the query string directly from user input with no validation, or other conversion, then the attacker has the ability to use any LDAP commands to query, filter, list, and crawl against the LDAP server directly in the same manner as SQL injection gives the ability to the attacker to run SQL commands on the database.

+ 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 3.2)
CAPEC Content TeamThe MITRE Corporation
Updated Related_Attack_Patterns
(Version 3.3)
CAPEC Content TeamThe MITRE Corporation
Updated Description, Mitigations
(Version 3.5)
CAPEC Content TeamThe MITRE Corporation
Updated Related_Weaknesses
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Page Last Updated or Reviewed: July 31, 2018