CWE-146 Detail

CWE-146

Improper Neutralization of Expression/Command Delimiters
Incomplete
2006-07-19
00h00 +00:00
2023-06-29
00h00 +00:00
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Name: Improper Neutralization of Expression/Command Delimiters

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as expression or command delimiters when they are sent to a downstream component.

CWE Description

As data is parsed, an injected/absent/malformed delimiter may cause the process to take unexpected actions.

General Informations

Modes Of Introduction

Implementation

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Common Consequences

Scope Impact Likelihood
Confidentiality
Integrity
Availability
Other
Execute Unauthorized Code or Commands, Alter Execution Logic

Potential Mitigations

Developers should anticipate that inter-expression and inter-command delimiters will be injected/removed/manipulated in the input vectors of their product. Use an appropriate combination of denylists and allowlists to ensure only valid, expected and appropriate input is processed by the system.
Phases : Implementation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.


Phases : Implementation
While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or 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).
Phases : Implementation
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.

Vulnerability Mapping Notes

Justification : This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Related Attack Patterns

CAPEC-ID Attack Pattern Name
CAPEC-15 Command Delimiters
An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or denylist input validation, as opposed to allowlist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or denylist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on.
CAPEC-6 Argument Injection
An attacker changes the behavior or state of a targeted application through injecting data or command syntax through the targets use of non-validated and non-filtered arguments of exposed services or methods.

NotesNotes

A shell metacharacter (covered in CWE-150) is one example of a potential delimiter that may need to be neutralized.

References

REF-62

The Art of Software Security Assessment
Mark Dowd, John McDonald, Justin Schuh.

Submission

Name Organization Date Date release Version
PLOVER 2006-07-19 +00:00 2006-07-19 +00:00 Draft 3

Modifications

Name Organization Date Comment
Eric Dalci Cigital 2008-07-01 +00:00 updated Potential_Mitigations, Time_of_Introduction
CWE Content Team MITRE 2008-09-08 +00:00 updated Relationships, Other_Notes, Taxonomy_Mappings
CWE Content Team MITRE 2008-10-14 +00:00 updated Description
CWE Content Team MITRE 2009-07-27 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2009-10-29 +00:00 updated Other_Notes, Relationship_Notes
CWE Content Team MITRE 2010-04-05 +00:00 updated Description, Name
CWE Content Team MITRE 2010-06-21 +00:00 updated Applicable_Platforms, Description, Relationship_Notes
CWE Content Team MITRE 2011-03-29 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2011-06-01 +00:00 updated Common_Consequences
CWE Content Team MITRE 2012-05-11 +00:00 updated References, Relationships
CWE Content Team MITRE 2012-10-30 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2014-07-30 +00:00 updated Relationships, Taxonomy_Mappings
CWE Content Team MITRE 2020-02-24 +00:00 updated Potential_Mitigations, Relationships
CWE Content Team MITRE 2020-06-25 +00:00 updated Potential_Mitigations
CWE Content Team MITRE 2023-01-31 +00:00 updated Description, Potential_Mitigations
CWE Content Team MITRE 2023-04-27 +00:00 updated Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes