CWE-921: Storage of Sensitive Data in a Mechanism without Access Control

Extended Description

While many modern file systems or devices utilize some form of access control in order to restrict access to data, not all storage mechanisms have this capability. For example, memory cards, floppy disks, CDs, and USB devices are typically made accessible to any user within the system. This can become a problem when sensitive data is stored in these mechanisms in a multi-user environment, because anybody on the system can read or write this data. On Android devices, external storage is typically globally readable and writable by other applications on the device. External storage may also be easily accessible through the mobile device's USB connection or physically accessible through the device's memory card port.

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Detect imprecise mappings involving CWE-921

Review mappings to CWE-921, Storage of Sensitive Data in a Mechanism without Access Control, with MITRE's mapping and navigation criteria. Flag any selection that points to a View or Category, remains at a higher abstraction than the available evidence supports, or ignores relevant parent, child, peer, and alternative entries. Treat those findings as mapping-quality defects, correct them before publication, and retain the comparison trail for repeatable audits.

CWE Mapping and Navigation Guidance — MITRE CWE

Prevent CWE-921 through an SSDF control plan

Use NIST SSDF practices to make prevention of CWE-921, Storage of Sensitive Data in a Mechanism without Access Control, 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 Technology

Triage CWE-921 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-921, Storage of Sensitive Data in a Mechanism without Access Control, 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 Agency

Use MITRE taxonomy anchors to review Storage of Sensitive Data in a Mechanism without Access Control

Recorded impacts include Read Application Data, Read Files or Directories, Modify Application Data, and Modify Files or Directories; related weaknesses include CWE-922. Use these source-defined anchors to turn CWE-921 into implementation, review, and verification checks for the affected component.

CWE-921: Storage of Sensitive Data in a Mechanism without Access Control — MITRE CWE

Validate CWE-921 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-921, Storage of Sensitive Data in a Mechanism without Access Control. 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 CWE

Frequently Asked Questions

What is CWE-921: Storage of Sensitive Data in a Mechanism without Access Control?+

CWE-921: Storage of Sensitive Data in a Mechanism without Access Control is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product stores sensitive information in a file system or device that does not have built-in access control. While many modern file systems or devices utilize some form of access control in order to restrict access to data, not all storage mechanisms have this capability. For example, memory cards, floppy disks, CDs, and USB devices are typically made accessible to any user within the system. This can become a problem when sensitive data is stored in these mechanisms in a multi-user environment, because anybody on the system can read or write this data. On Android devices, external storage is typically globally readable and writable by other applications on the device. External storage may also be easily accessible through the mobile device's USB connection or physically accessible through the device's memory card port.

What are the security consequences of Storage of Sensitive Data in a Mechanism without Access Control?+

If exploited, CWE-921 (Storage of Sensitive Data in a Mechanism without Access Control) it can compromise Confidentiality and Integrity, leading to outcomes such as Read Application Data, Read Files or Directories, Modify Application Data and Modify Files or Directories.

Which programming languages are affected by Storage of Sensitive Data in a Mechanism without Access Control?+

CWE-921 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What is the difference between a CWE and a CVE?+

A CWE (Common Weakness Enumeration) like CWE-921 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.

CWE-921: Storage of Sensitive Data in a Mechanism without Access Control

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