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CWE Reference

CWE-415: Double Free | Glexia

CWE-415 (Double Free) weakness overview with consequences, detection methods, mitigations, related CVEs and MITRE ATT&CK context.

Release 4.20weaknessDraft
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Glexia's Take · Automated analysis

CWE-415: Double-free

Double Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Executive Impact

  • Integrity Confidentiality Availability: Modify Memory Execute Unauthorized Code or Commands: When a program calls free() twice with the same argument, the program's memory management data structures may become corrupted, potentially leading to the reading or modification of unexpected memory addresses. This corruption can cause the program to crash or, in some circumstances, cause two later calls to malloc() to return the same pointer. If malloc() returns the same value twice and the program later gives the attacker control over the data that is written into this doubly-allocated memory, the program becomes vulnerable to a buffer overflow attack. Doubly freeing memory may result in a write-what-where condition, allowing an attacker to execute arbitrary code.

Developer Pattern

CWE-415 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.

Automation confidence

high confidence from CWE-415, 4.20.

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Official CWE Definition

CWE-415: Double Free

The product calls free() twice on the same memory address.

Type
weakness
Abstraction
Variant
Status
Draft
Source
MITRE CWE definition

Developer And Remediation Guidance

How teams prevent and detect this weakness

Causes

  • The following code shows a simple example of a double free vulnerability. Double free vulnerabilities have two common (and sometimes overlapping) causes: Error conditions and other exceptional circumstances Confusion over which part of the program is responsible for freeing the memory 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].

Mappings

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ATT&CK Relevance

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