COMMON WEAKNESS ENUMERATIONIncomplete

CWE-130

Improper Handling of Length Parameter Inconsistency

The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data.

Extended description

If an attacker can manipulate the length parameter associated with an input such that it is inconsistent with the actual length of the input, this can be leveraged to cause the target application to behave in unexpected, and possibly, malicious ways. One of the possible motives for doing so is to pass in arbitrarily large input to the application. Another possible motivation is the modification of application state by including invalid data for subsequent properties of the application. Such weaknesses commonly lead to attacks such as buffer overflows and execution of arbitrary code.

Terminology

Alternate terms and usages

length manipulation

length tampering

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Read MemoryModify MemoryVaries by Context

Affected security scopes: Confidentiality, Integrity

Defence

How is it prevented and fixed?

Implementation

Implementation-phase defence

Detail
When processing structured incoming data containing a size field followed by raw data, ensure that you identify and resolve any inconsistencies between the size field and the actual size of the data.

Implementation

Implementation-phase defence

Detail
Do not let the user control the size of the buffer.

Implementation

Implementation-phase defence

Detail
Validate that the length of the user-supplied data is consistent with the buffer size.

Verification

How is it detected?

Automated Static Analysis

High
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.)