CWE-226: Sensitive Information in Resource Not Removed Before Reuse
The product releases a resource such as memory or a file so that it can be made available for reuse, but it does not clear or "zeroize" the information contained in the resource before the product performs a critical state transition or makes the resource available for reuse by other entities.
How it's found
Sensitive Information in Resource Not Removed Before Reuse is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
When resources are released, they can be made available for reuse. For example, after memory is de-allocated, an operating system may make the memory available to another process, or disk space may be reallocated when a file is deleted. As removing information requires time and additional resources, operating systems do not usually clear the previously written information. Even when the resource is reused by the same process, this weakness can arise when new data is not as large as the old data, which leaves portions of the old data still available. Equivalent errors can occur in other situations where the length of data is variable but the associated data structure is not. If memory is not cleared after use, the information may be read by less trustworthy parties when the memory is reallocated. This weakness can apply in hardware, such as when a device or system switches between power, sleep, or debug states during normal operation, or when execution changes to different users or privilege levels.
Vulnerable vs. safe
During the transition from A to B, the device does not scrub the memory.For transition from state A to state B, remove information which should not be available once the transition is complete.Consequences
- Read Application Data
Mitigations
- 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.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-226?
The product releases a resource such as memory or a file so that it can be made available for reuse, but it does not clear or "zeroize" the information contained in the resource before the product performs a critical state transition or makes the resource available for reuse by other entities.
How do you find Sensitive Information in Resource Not Removed Before Reuse?
Sensitive Information in Resource Not Removed Before Reuse is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
What is the impact of CWE-226?
Read Application Data
Does TurboPentest test for Sensitive Information in Resource Not Removed Before Reuse?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
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Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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