Incomplete List of Disallowed Inputs
The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete, leading to resultant weaknesses.
Developers often try to protect their products against malicious input by performing tests against inputs that are known to be bad, such as special characters that can invoke new commands. However, such lists often only account for the most well-known bad inputs. Attackers may be able to find other malicious inputs that were not expected by the developer, allowing them to bypass the intended protection mechanism.
The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.
Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.
The following code attempts to stop XSS attacks by removing all occurences of "script" in an input string.
Because the code only checks for the lower-case "script" string, it can be easily defeated with upper-case script tags.
Weaknesses in this category are related to protection mechanism failure.
Weaknesses in this category are related to the A03 category "Injection" in the OWASP Top Ten 2021.
Weaknesses in this category are related to a software system's components for input validation, output validation, or other kinds of validation. Validation is a freque...
This view (slice) covers all the elements in CWE.
This view (slice) lists weaknesses that can be introduced during implementation.
This view (slice) lists weaknesses that can be introduced during design.