2137
Common Consequences
Scope Impact Likelihood
Other Varies by Context
Potential Mitigations
Phase: Implementation
Strategy = Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use
a list of acceptable inputs that strictly conform to specifications. Reject any input that does not
strictly conform to specifications, or transform it into something that does. When performing
input validation, consider all potentially relevant properties, including length, type of input, the
full range of acceptable values, missing or extra inputs, syntax, consistency across related
fields, and conformance to business rules. As an example of business rule logic, "boat" may be
syntactically valid because it only contains alphanumeric characters, but it is not valid if the input
is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for
malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if
the code's environment changes. This can give attackers enough room to bypass the intended
validation. However, denylists can be useful for detecting potential attacks or determining which
inputs are so malformed that they should be rejected outright.
Effectiveness = High
Demonstrative Examples
Example 1:
The following code loads and parses an XML file.
Example Language: Java (Bad)
// Read DOM
try {
...
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating( false );
....
c_dom = factory.newDocumentBuilder().parse( xmlFile );
} catch(Exception ex) {
...
}
The XML file is loaded without validating it against a known XML Schema or DTD.
Observed Examples
Reference Description
CVE-2016-4029 Chain: incorrect validation of intended decimal-based IP address format
(CWE-1286) enables parsing of octal or hexadecimal formats (CWE-1389),
allowing bypass of an SSRF protection mechanism (CWE-918).
https://www.cve.org/CVERecord?id=CVE-2016-4029
CVE-2007-5893 HTTP request with missing protocol version number leads to crash
https://www.cve.org/CVERecord?id=CVE-2007-5893
MemberOf Relationships
This MemberOf relationships table shows additional CWE Catgeories and Views that reference this
weakness as a member. This information is often useful in understanding where a weakness fits
within the context of external information sources.
CWE Version 4.14
CWE-1287: Improper Validation of Specified Type of Input
CWE-1287: Improper Validation of Specified Type of Input