CWE-226 Base Draft

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 previously contained. The old information remains accessible when…

Definition

What is CWE-226?

This vulnerability occurs when a system releases a resource like memory or a file for reuse but fails to erase the sensitive data it previously contained. The old information remains accessible when the resource is allocated to a new process or used in a different context.
When an operating system or application frees resources—such as deallocating memory or deleting a file—it typically doesn't automatically wipe the stored data for performance reasons. This leftover information can then be exposed if the resource is reused by another part of the system or a different user. The risk also appears within the same process, like when new variable-length data doesn't fully overwrite older, larger data, leaving remnants in memory structures or on disk. This flaw extends to hardware states, such as transitions between power, sleep, or debug modes, where residual data might leak across privilege boundaries. Proactively clearing sensitive data before reuse is a key defense. While SAST tools can detect these patterns, Plexicus uses AI to not only identify the issue but also generate the specific code fixes—like zeroizing memory or securely wiping files—saving significant manual remediation effort across your application portfolio.
Real-world impact

Real-world CVEs caused by CWE-226

  • CVE-2019-3733

    Cryptography library does not clear heap memory before release

  • CVE-2003-0001

    Ethernet NIC drivers do not pad frames with null bytes, leading to infoleak from malformed packets.

  • CVE-2003-0291

    router does not clear information from DHCP packets that have been previously used

  • CVE-2005-1406

    Products do not fully clear memory buffers when less data is stored into the buffer than previous.

  • CVE-2005-1858

    Products do not fully clear memory buffers when less data is stored into the buffer than previous.

  • CVE-2005-3180

    Products do not fully clear memory buffers when less data is stored into the buffer than previous.

  • CVE-2005-3276

    Product does not clear a data structure before writing to part of it, yielding information leak of previously used memory.

  • CVE-2002-2077

    Memory not properly cleared before reuse.

How attackers exploit it

Step-by-step attacker path

  1. 1

    This example shows how an attacker can take advantage of an incorrect state transition.

  2. 2

    Suppose a device is transitioning from state A to state B. During state A, it can read certain private keys from the hidden fuses that are only accessible in state A but not in state B. The device reads the keys, performs operations using those keys, then transitions to state B, where those private keys should no longer be accessible.

  3. 3

    After the transition to state B, even though the private keys are no longer accessible directly from the fuses in state B, they can be accessed indirectly by reading the memory that contains the private keys.

  4. 4

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

  5. 5

    There is an attempt to scrub the sensitive data from memory, but realloc() is used, so it could return a pointer to a different part of memory. The memory that was originally allocated for cleartext_buffer could still contain an uncleared copy of the data.

Vulnerable code example

Vulnerable Other

Suppose a device is transitioning from state A to state B. During state A, it can read certain private keys from the hidden fuses that are only accessible in state A but not in state B. The device reads the keys, performs operations using those keys, then transitions to state B, where those private keys should no longer be accessible.

Vulnerable Other 
During the transition from A to B, the device does not scrub the memory.
Secure code example

Secure Other

After the transition to state B, even though the private keys are no longer accessible directly from the fuses in state B, they can be accessed indirectly by reading the memory that contains the private keys.

Secure Other 
For transition from state A to state B, remove information which should not be available once the transition is complete.
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-226

  • Architecture and Design / Implementation During critical state transitions, information not needed in the next state should be removed or overwritten with fixed patterns (such as all 0's) or random data, before the transition to the next state.
  • Architecture and Design / Implementation When releasing, de-allocating, or deleting a resource, overwrite its data and relevant metadata with fixed patterns or random data. Be cautious about complex resource types whose underlying representation might be non-contiguous or change at a low level, such as how a file might be split into different chunks on a file system, even though "logical" file positions are contiguous at the application layer. Such resource types might require invocation of special modes or APIs to tell the underlying operating system to perform the necessary clearing, such as SDelete (Secure Delete) on Windows, although the appropriate functionality might not be available at the application layer.
Detection signals

How to detect CWE-226

Manual Analysis High

Write a known pattern into each sensitive location. Trigger the release of the resource or cause the desired state transition to occur. Read data back from the sensitive locations. If the reads are successful, and the data is the same as the pattern that was originally written, the test fails and the product needs to be fixed. Note that this test can likely be automated.

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 auto-detects CWE-226 and opens a fix PR in under 60 seconds.

Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.

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Frequently asked questions

Frequently asked questions

What is CWE-226?

This vulnerability occurs when a system releases a resource like memory or a file for reuse but fails to erase the sensitive data it previously contained. The old information remains accessible when the resource is allocated to a new process or used in a different context.

How serious is CWE-226?

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-226?

MITRE lists the following affected platforms: Not Technology-Specific.

How can I prevent CWE-226?

During critical state transitions, information not needed in the next state should be removed or overwritten with fixed patterns (such as all 0's) or random data, before the transition to the next state. When releasing, de-allocating, or deleting a resource, overwrite its data and relevant metadata with fixed patterns or random data. Be cautious about complex resource types whose underlying representation might be non-contiguous or change at a low level, such as how a file might be split into…

How does Plexicus detect and fix CWE-226?

Plexicus's SAST engine matches the data-flow signature for CWE-226 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-226?

MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/226.html. You can also reference OWASP and NIST documentation for adjacent guidance.

Related weaknesses

Weaknesses related to CWE-226

CWE-459 Parent

Incomplete Cleanup

This vulnerability occurs when an application fails to properly remove temporary files, data structures, or system resources after they…

CWE-460 Sibling

Improper Cleanup on Thrown Exception

This vulnerability occurs when a program fails to properly restore its state or release resources after an exception is thrown, leaving…

CWE-568 Sibling

finalize() Method Without super.finalize()

This vulnerability occurs when a Java class overrides the finalize() method but fails to call super.finalize() within it.

CWE-201 Can precede

Insertion of Sensitive Information Into Sent Data

This vulnerability occurs when an application sends data to an external party, but accidentally includes sensitive information—like…

CWE-1239 Child

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 Child

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 Child

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 Child

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-244 Child

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…

Resources

Further reading

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