Common Weakness Enumeration

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CWE-96: Improper Neutralization of Directives in Statically Saved Code ('Static Code Injection')

Weakness ID: 96
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The software receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before inserting the input into an executable resource, such as a library, configuration file, or template.
+ 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)
+ Relevant to the view "Architectural Concepts" (CWE-1008)
MemberOfCategoryCategory1019Validate Inputs
+ Relevant to the view "Development Concepts" (CWE-699)
+ Modes Of Introduction

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.

Architecture and DesignThis issue is most frequently found in PHP applications that allow users to set configuration variables that are stored within executable PHP files. Technically, this could also be performed in some compiled code (e.g. by byte-patching an executable), although it is highly unlikely.
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ 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.


PHP (Undetermined Prevalence)

Perl (Undetermined Prevalence)

Class: Interpreted (Undetermined Prevalence)

+ Common Consequences

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.


Technical Impact: Read Files or Directories; Read Application Data

The injected code could access restricted data / files.
Access Control

Technical Impact: Bypass Protection Mechanism

In some cases, injectable code controls authentication; this may lead to a remote vulnerability.
Access Control

Technical Impact: Gain Privileges or Assume Identity

Injected code can access resources that the attacker is directly prevented from accessing.

Technical Impact: Execute Unauthorized Code or Commands

Code injection attacks can lead to loss of data integrity in nearly all cases as the control-plane data injected is always incidental to data recall or writing. Additionally, code injection can often result in the execution of arbitrary code.

Technical Impact: Hide Activities

Often the actions performed by injected control code are unlogged.
+ Demonstrative Examples

Example 1

This example attempts to write user messages to a message file and allow users to view them.

(bad code)
Example Language: PHP 
$MessageFile = "cwe-94/messages.out";
if ($_GET["action"] == "NewMessage") {
$name = $_GET["name"];
$message = $_GET["message"];
$handle = fopen($MessageFile, "a+");
fwrite($handle, "<b>$name</b> says '$message'<hr>\n");
echo "Message Saved!<p>\n";

else if ($_GET["action"] == "ViewMessages") {


While the programmer intends for the MessageFile to only include data, an attacker can provide a message such as:

(attack code)

which will decode to the following:

(attack code)
<?php system("/bin/ls -l");?>

The programmer thought they were just including the contents of a regular data file, but PHP parsed it and executed the code. Now, this code is executed any time people view messages.

Notice that XSS (CWE-79) is also possible in this situation.

+ Observed Examples
Perl code directly injected into CGI library file from parameters to another CGI program.
Direct PHP code injection into supporting template file.
Direct code injection into PHP script that can be accessed by attacker.
PHP code from User-Agent HTTP header directly inserted into log file implemented as PHP script.
chain: execution after redirect allows non-administrator to perform static code injection.
+ Potential Mitigations

Phase: Implementation

Strategy: Input Validation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a whitelist 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 (i.e., do not rely on a blacklist). A blacklist 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, blacklists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Phase: Implementation

Strategy: Output Encoding

Perform proper output validation and escaping to neutralize all code syntax from data written to code files.
+ Weakness Ordinalities
(where the weakness exists independent of other weaknesses)
+ Affected Resources
  • File or Directory
+ 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.
MemberOfViewView884CWE Cross-section
MemberOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
+ Notes


"HTML injection" (see CWE-79: XSS) could be thought of as an example of this, but the code is injected and executed on the client side, not the server side. Server-Side Includes (SSI) are an example of direct static code injection.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERDirect Static Code Injection
Software Fault PatternsSFP24Tainted input to command
+ Content History
Submission DateSubmitterOrganization
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Potential_Mitigations, Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Relationships, Other_Notes, Taxonomy_Mappings, Weakness_Ordinalities
2009-05-27CWE Content TeamMITRE
updated Description, Name
2010-04-05CWE Content TeamMITRE
updated Description, Name
2010-06-21CWE Content TeamMITRE
updated Potential_Mitigations
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Common_Consequences, Demonstrative_Examples, Relationships
2012-10-30CWE Content TeamMITRE
updated Potential_Mitigations
2013-02-21CWE Content TeamMITRE
updated Observed_Examples
2014-06-23CWE Content TeamMITRE
updated Enabling_Factors_for_Exploitation, Other_Notes, Relationship_Notes
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-05-03CWE Content TeamMITRE
updated Related_Attack_Patterns
2017-11-08CWE Content TeamMITRE
updated Affected_Resources, Applicable_Platforms, Causal_Nature, Demonstrative_Examples, Enabling_Factors_for_Exploitation, Modes_of_Introduction, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Direct Static Code Injection
2009-05-27Insufficient Control of Directives in Statically Saved Code (Static Code Injection)
2010-04-05Improper Sanitization of Directives in Statically Saved Code ('Static Code Injection')

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Page Last Updated: January 18, 2018