CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection')

Description

Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory.

When sensitive data such as a password or an encryption key is not removed from memory, it could be exposed to an attacker using a "heap inspection" attack that reads the sensitive data using memory dumps or other methods. The realloc() function is commonly used to increase the size of a block of allocated memory. This operation often requires copying the contents of the old memory block into a new and larger block. This operation leaves the contents of the original block intact but inaccessible to the program, preventing the program from being able to scrub sensitive data from memory. If an attacker can later examine the contents of a memory dump, the sensitive data could be exposed.

Potential Impact

Demonstrative Examples

cleartext_buffer = get_secret();...cleartext_buffer = realloc(cleartext_buffer, 1024);...scrub_memory(cleartext_buffer, 1024);

Detection Methods

• Automated Static Analysis — 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 sea

Real-World CVE Examples

Related Weaknesses

Taxonomy Mappings

• 7 Pernicious Kingdoms: — Heap Inspection
• CERT C Secure Coding: MEM03-C — Clear sensitive information stored in reusable resources returned for reuse
• Software Fault Patterns: SFP23 — Exposed Data