Official definition

The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete.

Characteristics

Alternate terms

Denylist / Deny List — This is used by CWE and CAPEC instead of other commonly-used terms. Its counterpart is allowlist.
Blocklist / Block List — This is often used by security tools such as firewalls, email or web gateways, proxies, etc.
Blacklist / Black List — This term is frequently used, but usage has been declining as organizations have started to adopt other terms.

Modes of introduction

Implementation: Developers often try to protect their products against malicious input by checking against lists of known bad inputs, such as special characters that can invoke new commands. However, such lists often only address the most well-known bad inputs. As a quick fix, developers might rely on these lists instead of addressing the root cause of the issue. See [REF-141].
Architecture and Design: The design might rely solely on detection of malicious inputs as a protection mechanism.

Common consequences

Impact	Scope	Explanation
Bypass Protection Mechanism	Access Control	Attackers may be able to find other malicious inputs that were not expected by the developer, allowing them to bypass the intended protection mechanism.

Risk mitigations

Input Validation · ImplementationDo not rely exclusively on detecting disallowed inputs. There are too many variants to encode a character, especially when different environments are used, so there is a high likelihood of missing some variants. Only use detection of disallowed inputs as a mechanism for detecting suspicious activity. Ensure that you are using other protection mechanisms that only identify "good" input - such as lists of allowed inputs - and ensure that you are properly encoding your outputs.

Detection methods

Method	Approach	Effectiveness
Black Box	Exploitation of a vulnerability with commonly-used manipulations might fail, but minor variations might succeed.	-

Representative vulnerabilities

Below are representative vulnerabilities related to this CWE, prioritized by severity.

Sources (2)

MITRE CWE

CWE Terms of Use

CWE-184: Incomplete List of Disallowed Inputs

What is CWE-184?

Vulnerabilities mapped to CWE-184

Vulnerabilities in CISA KEV for CWE-184

Official definition

Characteristics

Alternate terms

Modes of introduction

Common consequences

Risk mitigations

Detection methods

Representative vulnerabilities

Supporting documents

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