420
filter all characters that do not pass an extremely strict allowlist (such as everything that is not
alphanumeric or white space). If some special characters are still needed, such as white space,
wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection
(CWE-88).
Phase: Implementation
Strategy = Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation
before being validated (CWE-180). Make sure that the application does not decode the same
input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by
introducing dangerous inputs after they have been checked.
Observed Examples
Reference Description
CVE-2002-1078 Directory listings in web server using multiple trailing slash
https://www.cve.org/CVERecord?id=CVE-2002-1078
CVE-2004-0281 Multiple trailing dot allows directory listing
https://www.cve.org/CVERecord?id=CVE-2004-0281
MemberOf Relationships
This MemberOf relationships table shows additional CWE Catgeories 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 Page
MemberOf 990 SFP Secondary Cluster: Tainted Input to Command 888 2413
MemberOf 1407 Comprehensive Categorization: Improper Neutralization 1400 2532
Taxonomy Mappings
Mapped Taxonomy Name Node ID Fit Mapped Node Name
PLOVER Multiple Trailing Special Elements
Software Fault Patterns SFP24 Tainted input to command
CWE-164: Improper Neutralization of Internal Special Elements
Weakness ID : 164
Structure : Simple
Abstraction : Variant
Description
The product receives input from an upstream component, but it does not neutralize or incorrectly
neutralizes internal special elements that could be interpreted in unexpected ways when they are
sent to a downstream component.
Extended Description
As data is parsed, improperly handled internal special elements may cause the process to take
unexpected actions that result in an attack.
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, MemberOr 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 may want to be explored.
Relevant to the view "Research Concepts" (CWE-1000)
CWE Version 4.14
CWE-164: Improper Neutralization of Internal Special Elements
CWE-164: Improper Neutralization of Internal Special Elements