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.
CWE-415 Variant Draft
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.
Auswirkungen in der Praxis
Real-world CVEs caused by CWE-415
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Chain: Signal handler contains too much functionality (CWE-828), introducing a race condition (CWE-362) that leads to a double free (CWE-415).
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Double free resultant from certain error conditions.
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Double free resultant from certain error conditions.
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Double free resultant from certain error conditions.
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Double free from invalid ASN.1 encoding.
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Double free from malformed GIF.
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Double free from malformed GIF.
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Double free from malformed compressed data.
Wie Angreifer es ausnutzen
Angreiferpfad Schritt für Schritt
- 1
The following code shows a simple example of a double free vulnerability.
- 2
Double free vulnerabilities have two common (and sometimes overlapping) causes:
- 3
- Error conditions and other exceptional circumstances - Confusion over which part of the program is responsible for freeing the memory
- 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
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.
char* ptr = (char*)malloc (SIZE);
...
if (abrt) {
free(ptr);
}
...
free(ptr); Sicheres Codebeispiel
Secure 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
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.)
CWE-415
Don't catalog this weakness. Prove it's reachable.
Plexicus turns CWE catalogs into evidence: every CWE-pattern is matched against your real code graph, reach is proven on a sandbox clone, and verified findings ship as reviewed PRs.
Häufig gestellte Fragen Was ist CWE-415?
Wie gravierend ist CWE-415?
Welche Sprachen oder Plattformen sind von CWE-415 betroffen?
Wie kann ich CWE-415 verhindern?
Wie erkennt und behebt Plexicus CWE-415?
Wo erfahre ich mehr über CWE-415?
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,…
Bereit, das Wesentliche zu validieren?
Bereit zu validieren, was zählt.
Plexicus ist Proof-Driven AppSec: validierte Funde, kontextuelles Verständnis und geprüfte Remediation — in Evidenz verankert, mit Ihnen gescoped.