CWE-415 Variant Draft High likelihood

Double Free

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.

Definition

What is CWE-415?

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.
This happens when a developer loses track of which pointers reference already-freed memory. The first free() call returns the memory to the system's pool for reuse, but the second call targets the same now-invalid address. This corrupts the memory manager's internal data structures, which can immediately crash the program or, more dangerously, create an opening for attackers to execute arbitrary code. Preventing double frees requires disciplined pointer management, such as setting pointers to NULL immediately after freeing them. While SAST tools can catch this pattern, Plexicus uses AI to suggest the actual code fix—like inserting that null assignment—saving hours of manual review and helping to secure your application's memory handling.
Vulnerability Diagram CWE-415
Double Free malloc p = 0x10A0 free(p) added to free-list free(p) again free-list corrupted Heap exploit arbitrary write The same chunk is freed twice → allocator metadata is poisoned.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-415

  • CVE-2006-5051

    Chain: Signal handler contains too much functionality (CWE-828), introducing a race condition (CWE-362) that leads to a double free (CWE-415).

  • CVE-2004-0642

    Double free resultant from certain error conditions.

  • CVE-2004-0772

    Double free resultant from certain error conditions.

  • CVE-2005-1689

    Double free resultant from certain error conditions.

  • CVE-2003-0545

    Double free from invalid ASN.1 encoding.

  • CVE-2003-1048

    Double free from malformed GIF.

  • CVE-2005-0891

    Double free from malformed GIF.

  • CVE-2002-0059

    Double free from malformed compressed data.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    The following code shows a simple example of a double free vulnerability.

  2. 2

    Double free vulnerabilities have two common (and sometimes overlapping) causes:

  3. 3

    - Error conditions and other exceptional circumstances - Confusion over which part of the program is responsible for freeing the memory

  4. 4

    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.

  5. 5

    While contrived, this code should be exploitable on Linux distributions that do not ship with heap-chunk check summing turned on.

Verwundbares Codebeispiel

Vulnerable C

The following code shows a simple example of a double free vulnerability.

Verwundbar C 
char* ptr = (char*)malloc (SIZE);
   ...
   if (abrt) { 
  	 free(ptr); 
   }
   ...
   free(ptr);
Sicheres Codebeispiel

Secure pseudo

Sicher pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste

How to prevent CWE-415

  • 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.
Erkennungssignale

How to detect CWE-415

Fuzzing High

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 High

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.)

Plexicus Auto-Fix

Plexicus erkennt CWE-415 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-415?

A double free vulnerability occurs when a program mistakenly calls the 'free()' function twice on the same block of memory.

Wie gravierend ist CWE-415?

MITRE stuft die Exploit-Wahrscheinlichkeit als hoch ein — diese Schwachstelle wird aktiv in freier Wildbahn ausgenutzt und sollte priorisiert behoben werden.

Welche Sprachen oder Plattformen sind von CWE-415 betroffen?

MITRE lists the following affected platforms: C, C++.

Wie kann ich CWE-415 verhindern?

Choose a language that provides automatic memory management. 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.

Wie erkennt und behebt Plexicus CWE-415?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-415 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-415?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/415.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-415

CWE-825 Parent

Expired Pointer Dereference

This vulnerability occurs when a program tries to use a pointer that still points to a memory location that has already been freed or…

CWE-416 Sibling

Use After Free

Use After Free happens when a program continues to use a pointer to a memory location after that memory has been freed. This can lead to…

CWE-123 Peer

Write-what-where Condition

A write-what-where condition occurs when an attacker can control both the data written and the exact memory location where it's written,…

Ressourcen

Further reading

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