CWE-241: Improper Handling of Unexpected Data Type

Source-backed guidance

Additional facts reviewed against primary or authoritative security sources.

Verify controls for CWE-241 with SSDF evidence

Use NIST SSDF verification and vulnerability-response practices to detect CWE-241, Improper Handling of Unexpected Data Type, throughout the product lifecycle. Derive review questions, static or dynamic checks, and negative tests from the CWE's causal behavior; define the components and lifecycle stages each check covers; and retain findings with enough evidence to distinguish the root cause from symptoms and impacts. Track escapes and false negatives, then improve the verification plan after every confirmed occurrence.

NIST SP 800-218 Secure Software Development Framework — National Institute of Standards and Technology

Apply Input Validation controls for Improper Handling of Unexpected Data Type

MITRE associates mitigation with Implementation; the listed strategies include Input Validation; recorded impacts include Varies by Context, and Unexpected State. Use these source-defined anchors to turn CWE-241 into implementation, review, and verification checks for the affected component.

CWE-241: Improper Handling of Unexpected Data Type — MITRE CWE

Triage CWE-241 against known exploitation evidence

Use CISA's Known Exploited Vulnerabilities catalog to test whether a vulnerability mapped to CWE-241, Improper Handling of Unexpected Data Type, 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

Apply precise root-cause mapping to CWE-241

Apply MITRE's full root-cause mapping guidance when using CWE-241, Improper Handling of Unexpected Data Type. 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 CWE

Validate CWE-241 with root-cause mapping checks

Apply MITRE's root-cause mapping quick tips to CWE-241, Improper Handling of Unexpected Data Type. 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-241: Improper Handling of Unexpected Data Type?+

CWE-241: Improper Handling of Unexpected Data Type is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product does not handle or incorrectly handles when a particular element is not the expected type, e.g. it expects a digit (0-9) but is provided with a letter (A-Z).

What are the security consequences of Improper Handling of Unexpected Data Type?+

If exploited, CWE-241 (Improper Handling of Unexpected Data Type) it can compromise Integrity and Other, leading to outcomes such as Varies by Context and Unexpected State.

Which programming languages are affected by Improper Handling of Unexpected Data Type?+

CWE-241 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.

What are real-world examples of Improper Handling of Unexpected Data Type?+

MITRE documents real CVEs mapped to CWE-241, including CVE-1999-1156 and CVE-2004-0270. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.

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

A CWE (Common Weakness Enumeration) like CWE-241 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-241: Improper Handling of Unexpected Data Type

Technical Details

Applicable To

Security Consequences

Scope

Impact

Mitigation Strategies

Detection Methods

Code Examples & CVEs

Observed CVE Examples (2)

CWE Relationships

Parent Weaknesses