CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Weakness ID: 74
The software constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
Software has certain assumptions about what constitutes data and control respectively. It is the lack of verification of these assumptions for user-controlled input that leads to injection problems. Injection problems encompass a wide variety of issues -- all mitigated in very different ways and usually attempted in order to alter the control flow of the process. For this reason, the most effective way to discuss these weaknesses is to note the distinct features which classify them as injection weaknesses. The most important issue to note is that all injection problems share one thing in common -- i.e., they allow for the injection of control plane data into the user-controlled data plane. This means that the execution of the process may be altered by sending code in through legitimate data channels, using no other mechanism. While buffer overflows, and many other flaws, involve the use of some further issue to gain execution, injection problems need only for the data to be parsed. The most classic instantiations of this category of weakness are SQL injection and format string vulnerabilities.
Time of Introduction
Architecture and Design
Technical Impact: Read application
Many injection attacks involve the disclosure of important information
-- in terms of both data sensitivity and usefulness in further
Technical Impact: Bypass protection
In some cases, injectable code controls authentication; this may lead
to a remote vulnerability.
Technical Impact: Alter execution
Injection attacks are characterized by the ability to significantly
change the flow of a given process, and in some cases, to the execution
of arbitrary code.
Technical Impact: Other
Data injection attacks lead to loss of data integrity in nearly all
cases as the control-plane data injected is always incidental to data
recall or writing.
Technical Impact: Hide activities
Often the actions performed by injected control code are
Likelihood of Exploit
Programming languages and supporting technologies might be chosen
which are not subject to these issues.
Utilize an appropriate mix of whitelist and blacklist parsing to
filter control-plane syntax from all input.
the weakness exists independent of other weaknesses)
In the development view (CWE-699), this is classified as an Input Validation problem (CWE-20) because many people do not distinguish between the consequence/attack (injection) and the protection mechanism that prevents the attack from succeeding. In the research view (CWE-1000), however, input validation is only one potential protection mechanism (output encoding is another), and there is a chaining relationship between improper input validation and the improper enforcement of the structure of messages to other components. Other issues not directly related to input validation, such as race conditions, could similarly impact message structure.