Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory.
View on MITREWhen 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.
Be careful using vfork() and fork() in security sensitive code. The process state will not be cleaned up and will contain traces of data from past use.
No mitigation information available for this CWE.
No detection method information available for this CWE.
The following code calls realloc() on a buffer containing sensitive data:
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.
cleartext_buffer = get_secret();...cleartext_buffer = realloc(cleartext_buffer, 1024);...scrub_memory(cleartext_buffer, 1024);Additional facts reviewed against primary or authoritative security sources.
Documented detection approaches include Automated Static Analysis; recorded impacts include Read Memory, and Other; observed examples include CVE-2019-3733. Use these source-defined anchors to turn CWE-244 into implementation, review, and verification checks for the affected component.
CWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection') — MITRE CWEUse NIST SSDF practices to make prevention of CWE-244, Improper Clearing of Heap Memory Before Release ('Heap Inspection'), an explicit development outcome. Translate the CWE definition into security requirements and design constraints, choose safer implementation patterns and toolchain checks, and define acceptance evidence before release. Feed every confirmed occurrence back into the requirements, design review, and coding rules so the same root cause is removed across the product rather than patched in one location.
NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and TechnologyUse CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-244, Improper Clearing of Heap Memory Before Release ('Heap Inspection'), has evidence of exploitation in the wild. Confirm the CVE-to-CWE root-cause mapping independently before attaching the example, then capture the affected product, required action, and remediation deadline. A missing KEV match is not evidence that the weakness is unexploited, and a KEV entry must not be generalized to every occurrence of this CWE.
Known Exploited Vulnerabilities Catalog — Cybersecurity and Infrastructure Security AgencyApply MITRE's full root-cause mapping guidance when using CWE-244, Improper Clearing of Heap Memory Before Release ('Heap Inspection'). Separate weakness language from attacker prerequisites and technical impact, check the entry's abstraction and vulnerability-mapping notes, and prefer the most specific Base or Variant supported by the evidence. Record the rejected alternatives and require an independent review before the mapping is used for remediation trends or program metrics.
CVE to CWE Root Cause Mapping Guidance — MITRE CWEApply MITRE's root-cause mapping quick tips to CWE-244, Improper Clearing of Heap Memory Before Release ('Heap Inspection'). Confirm the finding describes the causal weakness rather than an impact or attack pattern, compare the abstraction and mapping notes with plausible alternatives, and have a second reviewer challenge the selection. Preserve the evidence and reasoning so recurring defects can be measured against one consistent identifier.
CVE to CWE Root Cause Mapping Quick Tips — MITRE CWECWE-244: Improper Clearing of Heap Memory Before Release ('Heap Inspection') is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.
If exploited, CWE-244 (Improper Clearing of Heap Memory Before Release ('Heap Inspection')) it can compromise Confidentiality and Other, leading to outcomes such as Read Memory and Other.
CWE-244 commonly affects C, C++ and Memory-Unsafe. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
MITRE documents real CVEs mapped to CWE-244, including CVE-2019-3733. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-244 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.