CWE-672 Class Draft

Operation on a Resource after Expiration or Release

This vulnerability occurs when a program continues to use a resource—like memory, a file handle, or a network connection—after it has been freed, closed, or is no longer valid.

Definition

What is CWE-672?

This vulnerability occurs when a program continues to use a resource—like memory, a file handle, or a network connection—after it has been freed, closed, or is no longer valid.
Think of this as using a hotel key card after you've checked out. The system has marked that resource as available for reuse, but your code still holds a reference to it. When you try to read, write, or execute operations using this 'stale' reference, the results are unpredictable. The program might crash, leak sensitive data from the now-reallocated memory, or allow an attacker to hijack the resource for their own purposes. To prevent this, developers must carefully manage the lifecycle of all resources. This means ensuring that every 'malloc' has a matching 'free', every 'open' has a 'close', and that pointers or handles are set to NULL or another invalid state immediately after release. Using modern language features like smart pointers in C++ or try-with-resources in Java can automate this cleanup and make these dangerous 'use-after-free' and 'use-after-close' errors much less likely.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-672

  • CVE-2009-3547

    Chain: race condition (CWE-362) might allow resource to be released before operating on it, leading to NULL dereference (CWE-476)

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

    The following code shows a simple example of a use after free error:

  2. 2

    When an error occurs, the pointer is immediately freed. However, this pointer is later incorrectly used in the logError function.

  3. 3

    The following code shows a simple example of a double free error:

  4. 4

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

  5. 5

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

Verwundbares Codebeispiel

Vulnerable C

The following code shows a simple example of a use after free error:

Verwundbar C 
char* ptr = (char*)malloc (SIZE);
  if (err) {
  	abrt = 1;
  	free(ptr);
  }
  ...
  if (abrt) {
  	logError("operation aborted before commit", ptr);
  }
Sicheres Codebeispiel

Secure C

However, the call to the method logError includes the messageBody after the memory for messageBody has been released using the free method. This can cause unexpected results and may lead to system crashes. A variable should never be used after its memory resources have been released.

Sicher C 
...
  messageBody = (char*)malloc(length*sizeof(char));
  messageBody = &message[1][0];
  int success = processMessageBody(messageBody);
  if (success == ERROR) {
  	result = ERROR;
  	logError("Error processing message", messageBody);
  	free(messageBody);
  }
  ...
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-672

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Erkennungssignale

How to detect CWE-672

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-672 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-672?

This vulnerability occurs when a program continues to use a resource—like memory, a file handle, or a network connection—after it has been freed, closed, or is no longer valid.

Wie gravierend ist CWE-672?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-672 betroffen?

MITRE lists the following affected platforms: Mobile.

Wie kann ich CWE-672 verhindern?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

Wie erkennt und behebt Plexicus CWE-672?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-672 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-672?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/672.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-672

CWE-666 Parent

Operation on Resource in Wrong Phase of Lifetime

This vulnerability occurs when software interacts with a resource—like memory, a file, or a network connection—at an incorrect stage of…

CWE-415 Sibling

Double Free

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

CWE-593 Sibling

Authentication Bypass: OpenSSL CTX Object Modified after SSL Objects are Created

This vulnerability occurs when an application modifies an OpenSSL context object after it has already been used to create active SSL/TLS…

CWE-605 Sibling

Multiple Binds to the Same Port

This vulnerability occurs when a system's socket configuration allows multiple applications to bind to the same network port…

CWE-826 Sibling

Premature Release of Resource During Expected Lifetime

This happens when software incorrectly frees or closes a resource—like memory, a file handle, or a network connection—while that resource…

CWE-298 Child

Improper Validation of Certificate Expiration

This vulnerability occurs when an application fails to properly check if a digital certificate has expired, potentially trusting…

CWE-324 Child

Use of a Key Past its Expiration Date

This vulnerability occurs when an application continues to use a cryptographic key or password after its designated expiration date. Doing…

CWE-416 Child

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-613 Child

Insufficient Session Expiration

Insufficient session expiration occurs when an application allows old session tokens or IDs to remain valid for too long, letting…

Ressourcen

Further reading

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