An application uses a "blacklist" of prohibited values, but the blacklist is incomplete.
Extended Description
If an incomplete blacklist is used as a security mechanism, then the software may allow unintended values to pass into the application logic.
Relationships
The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
Nature
Type
ID
Name
ChildOf
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.
Variant - a weakness that is described at a very low level of detail, typically limited to a specific language or technology. More specific than a Base weakness.
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
Nature
Type
ID
Name
ChildOf
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase
Note
Implementation
Architecture and Design
Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Scope
Impact
Likelihood
Access Control
Technical Impact: Bypass Protection Mechanism
Demonstrative Examples
Example 1
The following code attempts to stop XSS attacks by removing all occurences of "script" in an input string.
(bad code)
Example Language: Java
public String removeScriptTags(String input, String mask) {
return input.replaceAll("script", mask);
}
Because the code only checks for the lower-case "script" string, it can be easily defeated with upper-case script tags.
"\" not in blacklist for web server, allowing path traversal attacks when the server is run in Windows and other OSes.
Potential Mitigations
Phase: Implementation
Strategy: Input Validation
Combine use of blacklist with appropriate use of whitelists.
Phase: Implementation
Strategy: Input Validation
Do not rely exclusively on blacklist validation to detect malicious input or to encode output. There are too many variants to encode a character; you're likely to miss some variants.
Weakness Ordinalities
Ordinality
Description
Primary
(where the weakness exists independent of other weaknesses)
Detection Methods
Black Box
Exploitation of incomplete blacklist weaknesses using the obvious manipulations might fail, but minor variations might succeed.
Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
An incomplete blacklist frequently produces resultant weaknesses.
Some incomplete blacklist issues might arise from multiple interpretation errors, e.g. a blacklist for dangerous shell metacharacters might not include a metacharacter that only has meaning in one particular shell, not all of them; or a blacklist for XSS manipulations might ignore an unusual construct that's supported by one web browser, but not others.
[REF-62] Mark Dowd, John McDonald
and Justin Schuh. "The Art of Software Security Assessment". Chapter 8, "Eliminating Metacharacters", Page 435. 1st Edition. Addison Wesley. 2006.
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Page Last Updated:
March 29, 2018
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Description
Relevant to the view "Research Concepts" (CWE-1000)
