Improper Validation of Consistency within Input
Incomplete Base
Structure: Simple
Description
The product receives a complex input with multiple elements or fields that must be consistent with each other, but it does not validate or incorrectly validates that the input is actually consistent.
Some input data can be structured with multiple elements or fields that must be consistent with each other, e.g. a number-of-items field that is followed by the expected number of elements. When such complex inputs are inconsistent, attackers could trigger unexpected errors, cause incorrect actions to take place, or exploit latent vulnerabilities.
Common Consequences 1
Scope: Other
Impact: Varies by Context
Potential Mitigations 1
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
Observed Examples 3
CVE-2018-16733product does not validate that the start block appears before the end block
CVE-2006-3790size field that is inconsistent with packet size leads to buffer over-read
CVE-2008-4114system crash with offset value that is inconsistent with packet size
Applicable Platforms
Languages:
Not Language-Specific : Often
Modes of Introduction
Implementation
Related Weaknesses
ChildOf:
Improper Input Validation (CWE-20)
Notes
MaintenanceThis entry is still under development and will continue to see updates and content improvements.