CWE-244 Variant Draft

Improper Clearing of Heap Memory Before Release ('Heap Inspection')

Using realloc() to resize buffers containing secrets like passwords or keys can leave that sensitive data exposed in memory, as the original data is not securely erased.

Definition

What is CWE-244?

Using realloc() to resize buffers containing secrets like passwords or keys can leave that sensitive data exposed in memory, as the original data is not securely erased.
When a program uses realloc() to enlarge a memory block, the system often allocates a new, larger chunk of memory and copies the old data over. The original memory block, still containing your sensitive information, becomes inaccessible to your program but remains physically present in the heap. This creates a dangerous window where the uncleared secrets are left behind, ripe for inspection. An attacker exploiting this weakness could perform a heap inspection attack by reading the process's memory through a dump or debugger. Since your code lost the pointer to the old location, it cannot overwrite that data, leaving passwords, encryption keys, or other confidential details fully visible to the attacker. To prevent this, you must manually clear sensitive data from a buffer before resizing it or use secure, dedicated functions designed for zeroing memory.
Real-world impact

Real-world CVEs caused by CWE-244

  • CVE-2019-3733

    Cryptography library does not clear heap memory before release

How attackers exploit it

Step-by-step attacker path

  1. 1

    Identify a code path that handles untrusted input without validation.

  2. 2

    Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.

  3. 3

    Deliver the payload through a normal request and observe the application's reaction.

  4. 4

    Iterate until the response leaks data, executes attacker code, or escalates privileges.

Vulnerable code example

Vulnerable C

The following code calls realloc() on a buffer containing sensitive data:

Vulnerable C 
cleartext_buffer = get_secret();...
  cleartext_buffer = realloc(cleartext_buffer, 1024);
  ...
  scrub_memory(cleartext_buffer, 1024);
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-244

  • 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.
Detection signals

How to detect CWE-244

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-244 and opens a fix PR in under 60 seconds.

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Frequently asked questions

Frequently asked questions

What is CWE-244?

Using realloc() to resize buffers containing secrets like passwords or keys can leave that sensitive data exposed in memory, as the original data is not securely erased.

How serious is CWE-244?

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-244?

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

How can I prevent CWE-244?

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.

How does Plexicus detect and fix CWE-244?

Plexicus's SAST engine matches the data-flow signature for CWE-244 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-244?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/244.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-244

CWE-226 Parent

Sensitive Information in Resource Not Removed Before Reuse

This vulnerability occurs when a system releases a resource like memory or a file for reuse but fails to erase the sensitive data it…

CWE-1239 Sibling

Improper Zeroization of Hardware Register

This vulnerability occurs when a hardware component fails to properly erase sensitive data from its internal registers before a new user…

CWE-1272 Sibling

Sensitive Information Uncleared Before Debug/Power State Transition

This vulnerability occurs when a device changes its power mode or enters a debug state but fails to wipe sensitive data that should become…

CWE-1301 Sibling

Insufficient or Incomplete Data Removal within Hardware Component

The product's data removal process fails to completely erase all data from hardware components, potentially leaving sensitive information…

CWE-1342 Sibling

Information Exposure through Microarchitectural State after Transient Execution

This vulnerability occurs when a CPU fails to completely erase temporary data traces left behind by speculative execution or error…

CWE-669 Can precede

Incorrect Resource Transfer Between Spheres

This vulnerability occurs when an application incorrectly moves or shares a resource (like data, permissions, or functionality) between…

Resources

Further reading

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