CWE-415: Double Free

Causes

• The following code shows a simple example of a double free vulnerability. Double free vulnerabilities have two common (and sometimes overlapping) causes:,[object Object],Although some double free vulnerabilities are not much more complicated than this example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.
• While contrived, this code should be exploitable on Linux distributions that do not ship with heap-chunk check summing turned on.

Remediation

• Architecture and Design: Choose a language that provides automatic memory management.
• 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.
• Implementation: Use a static analysis tool to find double free instances.

Detection

• 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.
• 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.)
• Automated Dynamic Analysis: Use tools that are integrated during compilation to insert runtime error-checking mechanisms related to memory safety errors, such as AddressSanitizer (ASan) for C/C++ [REF-1518].

Related CWEs

• CWE-364: Signal Handler Race Condition
• CWE-123: Write-what-where Condition
• CWE-1341: Multiple Releases of Same Resource or Handle
• CWE-416: Use After Free
• CWE-666: Operation on Resource in Wrong Phase of Lifetime
• CWE-672: Operation on a Resource after Expiration or Release
• CWE-672: Operation on a Resource after Expiration or Release
• CWE-672: Operation on a Resource after Expiration or Release
• CWE-825: Expired Pointer Dereference

Related CVEs

Related CVE mappings appear after CVE records are cross-indexed.

ATT&CK Relevance

ATT&CK relevance is shown only when reviewed or responsibly inferred.