1009
Nature Type ID Name Page
ChildOf 672 Operation on a Resource after Expiration or Release 1479
Applicable Platforms
Language : C (Prevalence = Undetermined)
Language : C++ (Prevalence = Undetermined)
Alternate Terms
Double-free :
Likelihood Of Exploit
High
Common Consequences
Scope Impact Likelihood
Integrity
Confidentiality
Availability
Modify Memory
Execute Unauthorized Code or Commands
Doubly freeing memory may result in a write-what-where
condition, allowing an attacker to execute arbitrary code.
Detection Methods
Fuzzing
Fuzz testing (fuzzing) is a powerful technique for generating large numbers of diverse inputs
- either randomly or algorithmically - and dynamically invoking the code with those inputs.
Even with random inputs, it is often capable of generating unexpected results such as crashes,
memory corruption, or resource consumption. Fuzzing effectively produces repeatable test cases
that clearly indicate bugs, which helps developers to diagnose the issues.
Effectiveness = High
Automated Static Analysis
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.)
Effectiveness = High
Potential Mitigations
Phase: Architecture and Design
Choose a language that provides automatic memory management.
Phase: Implementation
Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to
ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up
routines respect the state of allocation properly. If the language is object oriented, ensure that
object destructors delete each chunk of memory only once.
Phase: Implementation
Use a static analysis tool to find double free instances.
Demonstrative Examples
Example 1:
The following code shows a simple example of a double free vulnerability.
CWE Version 4.14
CWE-415: Double Free
CWE-415: Double Free