CWE-471: Modification of Assumed-Immutable Data (MAID)
Weakness ID: 471
The software does not properly protect an assumed-immutable element from being modified by an attacker.
This occurs when a particular input is critical enough to the functioning of the application that it should not be modifiable at all, but it is. Certain resources are often assumed to be immutable when they are not, such as hidden form fields in web applications, cookies, and reverse DNS lookups.
Time of Introduction
Architecture and Design
Technical Impact: Modify application
Common data types that are attacked are environment variables, web
application parameters, and HTTP headers.
Technical Impact: Unexpected state
In the code excerpt below, an array returned by a Java method is
modified despite the fact that arrays are mutable.
Gain privileges by modifying assumed-immutable
code addresses that are accessed by a driver.
Phases: Architecture and Design; Operation; Implementation
When the data is stored or transmitted through untrusted sources that
could modify the data, implement integrity checks to detect unauthorized
modification, or store/transmit the data in a trusted location that is
free from external influence.
MAID issues can be primary to many other weaknesses, and they are a major
factor in languages that provide easy access to internal program constructs,
such as PHP's register_globals and similar features. However, MAID issues
can also be resultant from weaknesses that modify internal state; for
example, a program might validate some data and store it in memory, but a
buffer overflow could overwrite that validated data, leading to a change in
There are many examples where the MUTABILITY property is a major factor in