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Automated Static Analysis
This weakness can often be detected using automated static analysis tools. Many modern tools
use data flow analysis or constraint-based techniques to minimize the number of false positives.
Effectiveness = Moderate
This is not a perfect solution, since 100% accuracy and coverage are not feasible.
Automated Dynamic Analysis
This weakness can be detected using dynamic tools and techniques that interact with the
software using large test suites with many diverse inputs, such as fuzz testing (fuzzing),
robustness testing, and fault injection. The software's operation may slow down, but it should not
become unstable, crash, or generate incorrect results.
Potential Mitigations
Phase: Architecture and Design
Strategy = Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides
constructs that make this weakness easier to avoid. For example, consider using the
ESAPI Encoding control [REF-45] or a similar tool, library, or framework. These will help the
programmer encode outputs in a manner less prone to error. Alternately, use built-in functions,
but consider using wrappers in case those functions are discovered to have a vulnerability.
Phase: Architecture and Design
Strategy = Parameterization
If available, use structured mechanisms that automatically enforce the separation between
data and code. These mechanisms may be able to provide the relevant quoting, encoding, and
validation automatically, instead of relying on the developer to provide this capability at every
point where output is generated. For example, stored procedures can enforce database query
structure and reduce the likelihood of SQL injection.
Phase: Architecture and Design
Phase: Implementation
Understand the context in which your data will be used and the encoding that will be expected.
This is especially important when transmitting data between different components, or when
generating outputs that can contain multiple encodings at the same time, such as web pages or
multi-part mail messages. Study all expected communication protocols and data representations
to determine the required encoding strategies.
Phase: Architecture and Design
In some cases, input validation may be an important strategy when output encoding is not a
complete solution. For example, you may be providing the same output that will be processed
by multiple consumers that use different encodings or representations. In other cases, you may
be required to allow user-supplied input to contain control information, such as limited HTML
tags that support formatting in a wiki or bulletin board. When this type of requirement must be
met, use an extremely strict allowlist to limit which control sequences can be used. Verify that
the resulting syntactic structure is what you expect. Use your normal encoding methods for the
remainder of the input.
Phase: Architecture and Design
Use input validation as a defense-in-depth measure to reduce the likelihood of output encoding
errors (see CWE-20).
Phase: Requirements
CWE Version 4.14
CWE-116: Improper Encoding or Escaping of Output
CWE-116: Improper Encoding or Escaping of Output