CWE-666 Class Draft

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 its existence, leading to crashes, data corruption, or…

Definition

What is CWE-666?

This vulnerability occurs when software interacts with a resource—like memory, a file, or a network connection—at an incorrect stage of its existence, leading to crashes, data corruption, or unpredictable behavior.
Every resource in a program has a distinct lifecycle: it's created (initialized), used for its intended purpose, and finally cleaned up (released). Each of these phases has specific rules. A common mistake is trying to use a resource before it's fully ready—like reading from an uninitialized memory buffer—or after it's been disposed of, such as closing an already-closed file handle. These operations violate the expected sequence and directly cause instability. To prevent this, developers must explicitly manage state. Ensure initialization is complete before use, validate the resource is in an 'active' state for operations, and avoid repeated or premature release. Using design patterns like RAII (Resource Acquisition Is Initialization) or implementing clear state flags can enforce the correct order and make invalid phase transitions obvious bugs during development.
Real-world impact

Real-world CVEs caused by CWE-666

  • 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).

How attackers exploit it

Step-by-step attacker path

  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.

Vulnerable code example

Vulnerable C

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

Vulnerable C 
char* ptr = (char*)malloc (SIZE);
   ...
   if (abrt) { 
  	 free(ptr); 
   }
   ...
   free(ptr);
Secure code example

Secure pseudo

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.
Prevention checklist

How to prevent CWE-666

  • Architecture and Design Follow the resource's lifecycle from creation to release.
Detection signals

How to detect CWE-666

SAST High

Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.

DAST Moderate

Run dynamic application security testing against the live endpoint.

Runtime Moderate

Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.

Code review Moderate

Code review: flag any new code that handles input from this surface without using the validated framework helpers.

Plexicus auto-fix

Plexicus auto-detects CWE-666 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-666?

This vulnerability occurs when software interacts with a resource—like memory, a file, or a network connection—at an incorrect stage of its existence, leading to crashes, data corruption, or unpredictable behavior.

How serious is CWE-666?

MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.

What languages or platforms are affected by CWE-666?

MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.

How can I prevent CWE-666?

Follow the resource's lifecycle from creation to release.

How does Plexicus detect and fix CWE-666?

Plexicus's SAST engine matches the data-flow signature for CWE-666 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.

Where can I learn more about CWE-666?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/666.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-666

CWE-664 Parent

Improper Control of a Resource Through its Lifetime

This vulnerability occurs when software fails to properly manage a resource throughout its entire lifecycle—from creation and active use…

CWE-118 Sibling

Incorrect Access of Indexable Resource ('Range Error')

This vulnerability occurs when software fails to properly check the boundaries of an indexed resource, like an array, buffer, or file,…

CWE-1229 Sibling

Creation of Emergent Resource

This vulnerability occurs when a system's normal operations unintentionally create new, exploitable resources that attackers can use to…

CWE-1250 Sibling

Improper Preservation of Consistency Between Independent Representations of Shared State

This vulnerability occurs when a system with multiple independent components (like distributed services or separate hardware units) each…

CWE-1329 Sibling

Reliance on Component That is Not Updateable

This vulnerability occurs when a product depends on a component that cannot be updated or patched to fix security flaws or critical bugs.

CWE-221 Sibling

Information Loss or Omission

This weakness occurs when an application fails to log critical security events or records them inaccurately, which can misguide security…

CWE-372 Sibling

Incomplete Internal State Distinction

This vulnerability occurs when an application fails to accurately track its own operational state. The system incorrectly assumes it's in…

CWE-400 Sibling

Uncontrolled Resource Consumption

This vulnerability occurs when an application fails to properly manage a finite resource, allowing an attacker to exhaust it and cause a…

CWE-404 Sibling

Improper Resource Shutdown or Release

This vulnerability occurs when a program fails to properly close or release a system resource—like a file handle, database connection, or…

Resources

Further reading

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