Improper Handling of Syntactically Invalid Structure

Incomplete Class

Structure: Simple

Description

The product does not handle or incorrectly handles input that is not syntactically well-formed with respect to the associated specification.

Common Consequences 1

Scope: IntegrityAvailability

Impact: Unexpected StateDoS: Crash, Exit, or RestartDoS: Resource Consumption (CPU)

If an input is syntactically invalid, then processing the input could place the system in an unexpected state that could lead to a crash, consume available system resources or other unintended behaviors.

Detection Methods 1

Automated Static AnalysisHigh

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Demonstrative Examples 1

ID : DX-110

This Android application has registered to handle a URL when sent an intent:

Code Example:

Bad

Java

...* IntentFilter filter = new IntentFilter("com.example.URLHandler.openURL"); MyReceiver receiver = new MyReceiver(); registerReceiver(receiver, filter);

java

java

The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.

Observed Examples 1

CVE-2004-0270Anti-virus product has assert error when line length is non-numeric.

Modes of Introduction

Implementation

Related Weaknesses

ChildOf:

Improper Check or Handling of Exceptional Conditions (CWE-703)

ChildOf:

Improper Neutralization (CWE-707)

Taxonomy Mapping

PLOVER
OWASP Top Ten 2004

Notes

MaintenanceThis entry needs more investigation. Public vulnerability research generally focuses on the manipulations that generate invalid structure, instead of the weaknesses that are exploited by those manipulations. For example, a common attack involves making a request that omits a required field, which can trigger a crash in some cases. The crash could be due to a named chain such as Unchecked Return Value to NULL Pointer Dereference (Unchecked Return Value to NULL Pointer Dereference), but public reports rarely cover this aspect of a vulnerability.

TheoreticalThe validity of input could be roughly classified along "syntactic", "semantic", and "lexical" dimensions. If the specification requires that an input value should be delimited with the "[" and "]" square brackets, then any input that does not follow this specification would be syntactically invalid. If the input between the brackets is expected to be a number, but the letters "aaa" are provided, then the input is syntactically invalid. If the input is a number and enclosed in brackets, but the number is outside of the allowable range, then it is semantically invalid. The inter-relationships between these properties - and their associated weaknesses- need further exploration.