1327
When free() is called on an invalid pointer, the program's memory management data structures
may become corrupted. This corruption can cause the program to crash or, in some circumstances,
an attacker may be able to cause free() to operate on controllable memory locations to modify
critical program variables or execute code.
Relationships
The table(s) below shows the weaknesses and high level categories that are related to this
weakness. These relationships are defined as ChildOf, ParentOf, MemberOr and give insight to
similar items that may exist at higher and lower levels of abstraction. In addition, relationships such
as PeerOf and CanAlsoBe are defined to show similar weaknesses that may want to be explored.
Relevant to the view "Research Concepts" (CWE-1000)
Nature Type ID Name Page
ChildOf 762 Mismatched Memory Management Routines 1596
CanPrecede 123 Write-what-where Condition 323
Common Consequences
Scope Impact Likelihood
Integrity
Confidentiality
Availability
Execute Unauthorized Code or Commands
Modify Memory
There is the potential for arbitrary code execution with
privileges of the vulnerable program via a "write, what
where" primitive. If pointers to memory which hold user
information are freed, a malicious user will be able to write
4 bytes anywhere in memory.
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: Implementation
Only free pointers that you have called malloc on previously. This is the recommended solution.
Keep track of which pointers point at the beginning of valid chunks and free them only once.
Phase: Implementation
Before freeing a pointer, the programmer should make sure that the pointer was previously
allocated on the heap and that the memory belongs to the programmer. Freeing an unallocated
pointer will cause undefined behavior in the program.
CWE Version 4.14
CWE-590: Free of Memory not on the Heap
CWE-590: Free of Memory not on the Heap